Reapply [InstCombine] Fold multiuse shr eq zero

This was reverted due to performance regressions in ARM benchmarks,
which have since been addressed by D101196 (SCEV analysis improvement)
and D101778 (CGP reverse transform).

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The single-use case is handled implicity by converting the icmp
into a mask check first. When comparing with zero in particular,
we don't need the one-use restriction, as we only produce a single
icmp.

https://alive2.llvm.org/ce/z/MSixcm
https://alive2.llvm.org/ce/z/GwpG0M