Backport AArch64 codegen improvements to r25c

[pirama-arumuga-nainar]

Description

Some AArch64 codegen improvements in LLVM are backported to the toolchain in the r25c LTS release.

• https://android-review.git.corp.google.com/c/toolchain/llvm_android/+/2259912
• https://android-review.git.corp.google.com/c/toolchain/llvm_android/+/2304180

Upstream bug

No response

Commit to cherry-pick

No response

Affected versions

r25

Canary version

No response

Host OS

Linux, Mac, Windows

Host OS version

N/A

Affected ABIs

arm64-v8a