Investigate whether it is worth it to enable XXH3_128bit build ids in LLVM, Mold and Binutils.

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Since #4570 and #4575 BLAKE3 hashes (truncated to 160 bits / 20 bytes) is now supported and is already a fair bit faster than SHA-1.

This issue is for documenting the speedup of XXH3_128bit vs. SHA-1 and BLAKE3 and then making a decision of whether this speedup is sufficient to make it worth pursuing.

See #1346 for context.