This bumps the checkpoint to height 518353.

The patch was removed as an input file during the release prep version
bump.

Versions bump and Changelog update

Remove firefox-locale-bundle and remaining mobile bits in the firefox
project.

Update fenix

Update documentation on how to fetch Gradle dependencies

Update android-components

We additionally clean up our build script so that we actually only
compile the browser engine code we want to be compiled (the build
breaks otherwise due to GeckoView mismatch which caused us to exempt
geckoview-nightly from getting overwritten by our own earlier on).

Update application-services

This reverts commit 82ad6be5.

We need to bump Rust to 1.45 for #40115 and thus, we need to back out
this patch again and try finding a fix for #40114 instead.

Update GeckoView part

application-services needs a newer Rust compiler as it now uses
features (strip_suffix()) that got stablizied in 1.45.0 first. We don't
want to risk GeckoView stability and thus bite the bullet and add a
different project solely used by application-services for the time being.
We omit the clean-up as this is supposed to be temporary until Rust for
GeckoView gets bumped.

It is noteworthy that we still need the patch for bug 43909 albeit in
a slightly updated fashion. Originally, this landed on trunk for the
10.0 release but it got backed out later on and did not reland in time
for any 10.0 release. Thus, we need to keep that patch until Rust
switches to LLVM 11.

As Fenix 82 uses clang 11.0.0-rc3 it is easier if we switch to using
the llvm-project repository directly. This fixes the mobile part of
bug 40048.

We need to use our compiled binutils version, too, as the one that comes
with Debian Buster (2.31.1) is breaking the build. We hit
https://bugs.llvm.org/show_bug.cgi?id=42994 which is essentially
an ld bug (https://sourceware.org/bugzilla/show_bug.cgi?id=24458). That
one is fixed on the 2.31 branch and onwards but never made it into a
2.31.x release.

We can drop our Windows patches now as the underlying bug
(https://sourceware.org/bugzilla/show_bug.cgi?id=17321) got fixed
in binutils 2.34.