[mlir][linalg][bufferize] Implement equivalence analysis

Instead of checking buffer equivalence during bufferization, gather buffer equivalence information right after the analysis. This is in preparation of decoupling bufferization from BufferizationAliasInfo.

This change also fixes equivalence analysis for scf.if op results, which was not fully implemented. scf.if op results are equivalent to their corresponding yield values if both yield values are equivalent.

Differential Revision: https://reviews.llvm.org/D114774