[mlir][linalg][bufferize][NFC] Add `analyzeOp` helper function

This function runs just the analysis of Comprehensive Bufferize, but does not bufferize the IR yet.

This is in preparation of fixing CallOp bufferization. Also needed for unifying Comprehensive Bufferize and core bufferization; the new partial bufferization can simply run bufferization without an analysis.

Differential Revision: https://reviews.llvm.org/D116456