rustdoc: add hash to filename of toolchain files

[jsha]

All static files used by rustdoc are now stored in static.files/ and their filenames include a hash of their contents. Their filenames no longer include the contents of the --resource-suffix flag. This clarifies caching semantics. Anything in static.files can use Cache-Control: immutable because any updates will show up as a new URL.

Invocation-specific files like crates-NN.js, search-index-NN.js, and sidebar-items-NN.js still get the resource suffix.

This has a useful side effect: once toolchain files aren't affected by resource suffix, it will become possible for docs.rs to include crate version in the resource suffix. That should fix a caching issue with /latest/ URLs: rust-lang/docs.rs#1593. My goal is that it should be safe to serve all rustdoc JS, CSS, and fonts with infinite caching headers, even when new versions of a crate are uploaded in the same place as old versions.

The --disable-minification flag is removed because it would vary the output of static files based on invocation flags. Instead, for rustdoc development purposes it's preferable to symlink static files to a non-minified copy for quick iteration.

Example listing:

$ cd build/x86_64-unknown-linux-gnu/doc/ && find . | egrep 'js$|css$' | egrep -v 'sidebar-items|implementors' | sort
./crates1.65.0.js
./rust.css
./search-index1.65.0.js
./source-files1.65.0.js
./static.files/ayu-2bfd0af01c176fd5.css
./static.files/dark-95d11b5416841799.css
./static.files/light-c83a97e93a11f15a.css
./static.files/main-efc63f77fb116394.js
./static.files/normalize-76eba96aa4d2e634.css
./static.files/noscript-5bf457055038775c.css
./static.files/rustdoc-7a422337900fa894.css
./static.files/scrape-examples-3dd10048bcead3a4.js
./static.files/search-47f3c289722672cf.js
./static.files/settings-17b08337296ac774.js
./static.files/settings-3f95eacb845293c0.css
./static.files/source-script-215e9db86679192e.js
./static.files/storage-26d846fcae82ff09.js

Fixes #98413