This commit adds several fixes and improvements for the Zig compiler
test harness.

1. -Dskip-translate-c option added for skipping the translate-c tests.
2. translate-c/run-translated-c tests in test/cases/* have been added to
   the steps test-translate-c and test-run-translated-c. Closes #18224.
3. Custom name added to the CheckFile step for the translate-c step to
   better communicate which test failed.
4. Test manifest key validation added to return an error if a manifest
   contains an invalid key.