[MLIR] Fix crash in inliner when return arity mismatches call results (#185037)
The `handleTerminator` implementation in the test dialect's inliner
interface was asserting that the number of `test.return` operands equals
the number of values to replace. This assertion fires when inlining a
callee whose body uses `test.return` with values into a call site that
expects zero results (e.g., a void `llvm.func` calling a function whose
implementation uses `test.return` with operands).
Replace the assertion with a conditional early return so the inliner
gracefully skips replacement instead of crashing.
Fixes #108376
Assisted-by: Claude Code