Update PHP and Ruby amalgamations in regenerate_stale_files.sh

This removes the need for us to manually rebuild these amalgamation files. I
added the "manual" tag to the corresponding staleness tests so that we won't
get presubmit errors if the amalgamation files are out of date. I also had to
tweak the Ruby BUILD.bazel file to make sure it uses Bazel-generated
amalgamations instead of relying on the checked-in files.

I added deliberate errors to the Ruby and PHP amalgamation files to test that
everything is working. We should not see any CI errors, and the files should
quickly be auto-updated after the change lands on main.

PiperOrigin-RevId: 561187352