run_go_field_chain_sequential tears down the results, registry and
cross arenas but never calls harness_ctx_free_tables, so pass_calls'
CBMReturnTypeTable (strdup'd method return types) leaked whenever the
helper ran. ASan builds caught it: AddressSanitizer: 32911 byte(s)
leaked in 6 allocation(s) from build_return_type_table, failing
test-diag, test-lsan-macos and both gcc sanitizer shards. Verify
locally: build/c/test-runner parallel -> 73 passed, no leaks.
Signed-off-by: xkchok <143325001+xkchok@users.noreply.github.com>