[llvm] Add a super simple wrapper for a merged string table. (PR #119488)

[Jay Foad via llvm-commits]

jayfoad wrote:

Note that we already have `include/llvm/TableGen/StringToOffsetTable.h` and `utils/TableGen/Basic/SequenceToOffsetTable.h`. It would be good to consolidate all of these somehow, bearing in mind that there are different use cases: sequence types other than "string", sequences that don't need a terminator, sequences that should share common suffixes where possible, etc.

https://github.com/llvm/llvm-project/pull/119488