[llvm-branch-commits] [BOLT] Eliminate dead jump tables (PR #91666)

[Amir Ayupov via llvm-branch-commits]

https://github.com/aaupov created https://github.com/llvm/llvm-project/pull/91666

Dead jump tables such as those arising from FIXED_PIC_BRANCH
optimization don't need to be updated or moved. Further, if any jump
table entry points to a block removed by unreachable code elimination,
we would be unable to update it and jump table emission would fail.

Identify non-referenced jump tables and delete them to prevent that.

Test Plan: NFC for existing tests.