…inlining

When the MLIR inliner inlines a callable region that has more than one
block, it calls `handleTerminator(op, Block *newDest)` for the terminator
of every inlined block.  `TestInlinerInterface` only implemented the
single-block variant (`handleTerminator(op, ValueRange)`), so the
default `llvm_unreachable` was hit when inlining a `test.functional_region_op`
whose body contained multiple blocks (e.g. an explicit `cf.br` jump to a
successor block whose terminator was `test.return`).

Fix: add the missing `handleTerminator(op, Block *)` override to
`TestInlinerInterface`.  Mirror the pattern used by
`FuncDialectInlinerExtension`: if the terminator is a `TestReturnOp`,
replace it with a `cf.br` to `newDest` carrying the return operands.
Any other terminator (e.g. `cf.br` for intra-region branches) is left
untouched — the existing `ControlFlowInlinerInterface` no-op already
handles those correctly.

Add a regression test in `test/Transforms/inlining.mlir` that inlines a
`call_indirect` into a `test.functional_region_op` with two blocks.

Fixes llvm#185350

Assisted-by: Claude Code