Investigate why debug check on tests-mysql container fails

[kmanijak]

Description

Unit test PHP job on GitHub actions started to fail on 11 June.

That was due to debug check:

npm run wp-env run tests-mysql "mysql --version"

which resulted in the following:

OCI runtime exec failed: exec failed: unable to start container process: exec: "mysql": executable file not found in $PATH: unknown
✖ Command failed with exit code 126
Command failed with exit code 126
Error: Process completed with exit code 1.

That problem prevented PHP unit tests from being run. Example job.

In #9791 the problematic line was temporarily disabled, so the PHP tests could be run, however there is no clear reason why the check started fail (no changes in terms of @wordpress/env version which provides the container, nor the image or runner version).

This issues is to debug the problem and re-enable the commented line.