RUST-2058 Fix BSON WASM tests

[abr-egn]

RUST-2058

There were two unrelated issues here:

• The wasm32-wasi target was renamed in newer versions of rustc to wasm32-wasip1 (to make room for the upcoming wasm32-wasip2), so we need conditional logic for that.
• The version of LLVM used in rustc 1.82+ emits webassembly using a reference types specification that's not supported in the node.js runtime (this bug has some details). I've pinned that test to rustc 1.81 for now; hopefully by the time our MSRV catches up to that and we need to unpin it node will have also caught up :)

[kevinAlbs]

Nice, LGTM!