Revert "Roll clang+rust llvmorg-20-init-13894-g8cb44859-1 : llvmorg-20-init-16062-g091448e3-1 / a522d78598415cdd614ccc6d961160f192f64b5c-1 : 8a1f8039a7ded79d3d4fe97b110016d89f2b11e2-1"

This reverts commit 32fd5de30ad9dcb9d47816e97161de85b36b63c6.

Reason for revert: tree-closing compilation failures:
https://ci.chromium.org/ui/p/chromium/builders/ci/linux-cast-arm-rel/10744
https://ci.chromium.org/ui/p/chromium/builders/ci/linux-cast-arm64-rel/11108
https://ci.chromium.org/ui/p/chromium/builders/ci/linux-cast-x64-rel/6736
with the error:
chromecast/browser/cast_web_contents_impl.h:182:26: error: private field 'parent_cast_web_contents_' is not used [-Werror,-Wunused-private-field]
  182 |   CastWebContents* const parent_cast_web_contents_ = nullptr;

Original change's description:
> Roll clang+rust llvmorg-20-init-13894-g8cb44859-1 : llvmorg-20-init-16062-g091448e3-1 / a522d78598415cdd614ccc6d961160f192f64b5c-1 : 8a1f8039a7ded79d3d4fe97b110016d89f2b11e2-1
>
> https://chromium.googlesource.com/external/github.com/llvm/llvm-project/+log/8cb44859..091448e3
>
> https://chromium.googlesource.com/external/github.com/rust-lang/rust/+log/a522d7859841..8a1f8039a7de
>
> Ran: ./tools/clang/scripts/upload_revision.py 091448e3c17bc8e7812dd7b571c852576d648977
>
> Additionally:
> * Ran tools/rust/gnrt_stdlib.py
> * Updated //chrome/android/static_initializers.gni because it referred
>   to a static initializer in sme-abi-init.c, a file in compiler-rt that
>   was removed in llvm/llvm-project#119414.
>
> Bug: 382540640
> Disable-Rts: True
> Change-Id: I4fd6f81827ed519770048adb74430e8ec1fd849d
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6111009
> Auto-Submit: Alan Zhao <[email protected]>
> Commit-Queue: Zequan Wu <[email protected]>
> Commit-Queue: Alan Zhao <[email protected]>
> Reviewed-by: Zequan Wu <[email protected]>
> Cr-Commit-Position: refs/heads/main@{#1399472}

Bug: 382540640
Change-Id: Ib8d123e61472090b0643b5617aa7a259abd8ff58
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6108066
Owners-Override: David Baron <[email protected]>
Auto-Submit: David Baron <[email protected]>
Commit-Queue: Rubber Stamper <[email protected]>
Bot-Commit: Rubber Stamper <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1399476}
NOKEYCHECK=True
GitOrigin-RevId: dca68566e7efca3368542b8329cad45e875ba0ae

Author: dbaron

update_rust.py

@@ -31,7 +31,7 @@
 
 # These fields are written by //tools/clang/scripts/upload_revision.py, and
 # should not be changed manually.
-RUST_REVISION = '8a1f8039a7ded79d3d4fe97b110016d89f2b11e2'
+RUST_REVISION = 'a522d78598415cdd614ccc6d961160f192f64b5c'
 RUST_SUB_REVISION = 1
 
 # The revision of Crubit to use from https://github.com/google/crubit