Revert "prepopulate CARGO_HOME caches"

[TriplEight]

Reverts #5505
Apparently, cache pre-population from other branches with other versions of deps can cause the cargo bug.
To avoid it, everyone should rebase on this commit.

Logs

thread 'main' panicked at 'packages downloaded: failed to download `hermit-abi v0.1.10`
Caused by:
    0: unable to get packages from source
    1: failed to parse manifest at `/ci-cache/substrate/cargo/5515/check-web-wasm/registry/src/github.com-1ecc6299db9ec823/hermit-abi-0.1.10/Cargo.toml`
    2: no targets specified in the manifest
         either src/lib.rs, src/main.rs, a [lib] section, or [[bin]] section must be present
   0: cargo::ops::cargo_read_manifest::read_package
   1: cargo::sources::path::PathSource::read_packages
   2: <cargo::sources::path::PathSource as cargo::core::source::Source>::update
   3: cargo::sources::registry::RegistrySource::get_pkg
   4: <cargo::sources::registry::RegistrySource as cargo::core::source::Source>::download
   5: cargo::core::package::Downloads::start
   6: cargo::core::package::PackageSet::get_one
   7: core::iter::traits::iterator::Iterator::try_fold
   8: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold
   9: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
  10: cargo::core::resolver::features::FeatureResolver::activate_pkg
  11: cargo::core::resolver::features::FeatureResolver::activate_fv
  12: cargo::core::resolver::features::FeatureResolver::activate_rec
  13: cargo::core::resolver::features::FeatureResolver::activate_fv
  14: cargo::core::resolver::features::FeatureResolver::activate_rec
  15: cargo::core::resolver::features::FeatureResolver::activate_pkg
  16: cargo::core::resolver::features::FeatureResolver::activate_pkg
  17: cargo::core::resolver::features::FeatureResolver::activate_pkg
  18: cargo::core::resolver::features::FeatureResolver::activate_pkg
  19: cargo::core::resolver::features::FeatureResolver::activate_fv
  20: cargo::core::resolver::features::FeatureResolver::activate_rec
  21: cargo::core::resolver::features::FeatureResolver::activate_pkg
  22: cargo::core::resolver::features::FeatureResolver::resolve
  23: cargo::ops::resolve::resolve_ws_with_opts
  24: cargo::ops::cargo_compile::compile_ws
  25: cargo::ops::cargo_compile::compile
  26: cargo::commands::build::exec
  27: cargo::cli::main
  28: cargo::main
  29: std::rt::lang_start::{{closure}}
  30: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:52
      std::panicking::try::do_call
             at src/libstd/panicking.rs:331
      std::panicking::try
             at src/libstd/panicking.rs:274
      std::panic::catch_unwind
             at src/libstd/panic.rs:394
      std::rt::lang_start_internal
             at src/libstd/rt.rs:51
  31: main
  32: __libc_start_main
  33: <unknown>', src/tools/cargo/src/cargo/core/resolver/features.rs:573:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1069
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1439
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:511
  11: rust_begin_unwind
             at src/libstd/panicking.rs:419
  12: core::panicking::panic_fmt
             at src/libcore/panicking.rs:111
  13: core::option::expect_none_failed
             at src/libcore/option.rs:1268
  14: core::iter::traits::iterator::Iterator::try_fold
  15: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold
  16: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
  17: cargo::core::resolver::features::FeatureResolver::activate_pkg
  18: cargo::core::resolver::features::FeatureResolver::activate_fv
  19: cargo::core::resolver::features::FeatureResolver::activate_rec
  20: cargo::core::resolver::features::FeatureResolver::activate_fv
  21: cargo::core::resolver::features::FeatureResolver::activate_rec
  22: cargo::core::resolver::features::FeatureResolver::activate_pkg
  23: cargo::core::resolver::features::FeatureResolver::activate_pkg
  24: cargo::core::resolver::features::FeatureResolver::activate_pkg
  25: cargo::core::resolver::features::FeatureResolver::activate_pkg
  26: cargo::core::resolver::features::FeatureResolver::activate_fv
  27: cargo::core::resolver::features::FeatureResolver::activate_rec
  28: cargo::core::resolver::features::FeatureResolver::activate_pkg
  29: cargo::core::resolver::features::FeatureResolver::resolve
  30: cargo::ops::resolve::resolve_ws_with_opts
  31: cargo::ops::cargo_compile::compile_ws
  32: cargo::ops::cargo_compile::compile
  33: cargo::commands::build::exec
  34: cargo::cli::main
  35: cargo::main
  36: std::rt::lang_start::{{closure}}
  37: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:52
  38: std::panicking::try::do_call
             at src/libstd/panicking.rs:331
  39: std::panicking::try
             at src/libstd/panicking.rs:274
  40: std::panic::catch_unwind
             at src/libstd/panic.rs:394
  41: std::rt::lang_start_internal
             at src/libstd/rt.rs:51
  42: main
  43: __libc_start_main
  44: <unknown>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
real	0m0.642s
user	0m0.436s
sys	0m0.181s

Will think of how to reimplement the work around the bug. Maybe cargo vendor can help here.

In the meanwhile, every new branch's job on a new host will download and unpack all the deps from scratch.