Revert "[llvm][IR] Extend BranchWeightMetadata to track provenance of weights" (#95060)

Reverts llvm/llvm-project#86609

This change causes compile-time regressions for stage2 builds
(https://llvm-compile-time-tracker.com/compare.php?from=3254f31a66263ea9647c9547f1531c3123444fcd&to=c5978f1eb5eeca8610b9dfce1fcbf1f473911cd8&stat=instructions:u).
It also introduced unintended changes to `.text` which should be
addressed before relanding.