[clang] [llvm] [AArch64] Make +pauth enabled in Armv8.3-a by default (PR #78027)

[Anatoly Trosinenko via cfe-commits]

atrosinenko wrote:

Merged despite buildkite failure as its "Linux x64" job succeeded and "Windows x64" failed with an unrelated error :)

```
mt.exe : general error c101008d: Failed to write the updated manifest to the resource of file "tools\mlir\unittests\ExecutionEngine\MLIRExecutionEngineTests.exe". Operation did not complete successfully because the file contains a virus or potentially unwanted software.
```

https://github.com/llvm/llvm-project/pull/78027