[llvm-branch-commits] [Remarks] BitstreamRemarkParser: Refactor error handling (PR #156511)

[Tobias Stadler via llvm-branch-commits]

https://github.com/tobias-stadler created https://github.com/llvm/llvm-project/pull/156511

In preparation of larger changes to the bitstream remark format,
refactor the error handling code in the BitstreamRemarkParser.

Main change: move the various static helper methods into the parser
helper classes, so we don't need to pass around as many args. Calling
`error(...)` inside the helper classes now automatically prepends the
current block being parsed to the error message.

NFCI (except for error messages on invalid bitstream files).