meson: Update our rust dependencies
These are the package versions currently shipped by Fedora. This allows using system packages by setting
export MESON_PACKAGE_CACHE_DIR=/usr/share/cargo/registry/
Of course, other distros may place it somewhere else.
Ubuntu matches versions on syn and unicode-ident but is a tiny bit off on quote and proc-macro2. However, given how far I was able to bump the versions with only a tiny meson tweak to syn, I think it should work with the Ubuntu versions as well.