Auto merge of #108534 - Mark-Simulacrum:compression, r=pietroalbini

Import rust-installer & adjust compression settings

This brings in rust-lang/rust-installer#123, which enables a larger compression window (8 -> 64MB) amongst other changes to the xz compression settings. The net effect should be smaller compressed tarballs which will decrease bandwidth usage for
static.rust-lang.org, download times, and decompression time.

This comes at the cost of higher baseline requirements for running rustup to use these files, which we believe should be largely acceptable (running rustc is likely to use at least this much memory) but if we get specific reports we may explore options to decrease impact (e.g., using the gzip tarballs automatically in rustup).

To simplify iteration on compression settings this also imports the rust-lang/rust-installer submodule, it is now hosted fully inside rust-lang/rust. Once we land this I'll file a followup to add a note to that repo and we can subsequently archive it.

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CI times for dist-x86_64-linux builds:

* threads=6, master - 2h 50m
* threads=1, new - 3h 40m
* threads=6, new - 2h 50m

Author: bors