All static files used by rustdoc are now stored in static.files/ and
include a hash of their contents. They 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.
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.
