fix: emit source_loc around iterator_close so for/of return() stack traces report correct line

[mvanhorn]

Summary

When a for/of loop early-exits (break/return inside the body) saghul's iterator_close op runs to release the iterator. Any error thrown from the iterator's return() method was reported with the source_loc of the bytecode AFTER the loop, not the line of the actual for/of. Fix is to emit a source_loc op around iterator_close so the stack trace points at the loop.

Why this matters

Reporter pinpointed the exact OP and gave a minimal repro. The misleading line number made these errors very hard to diagnose, especially in generators where the iterator's return() can fail far from the call site.

Changes

• quickjs.c::js_for_of_close_callback (and the bytecode emitter) - bracket iterator_close with source_loc ops carrying the line of the originating for/of.

Testing

make all && ./run-test262 -c tests/test262.conf clean. Added a script case under tests/bugs that asserts the stack trace line matches the for/of source line.

Fixes #1266