Add support for arbitrary user IDs in secured Kubernetes environments without needing to disable permission checks.

#12905 added support for arbitrary user IDs, but it changed the permissions of the files in a way that require Beats docker images to be run with BEAT_STRICT_PERMS=false, what is not recommended so far.

We should find a way to support arbitrary user IDs, without changing the current behaviour for the rest of cases.

Related issues:

• Allow the Docker image to be run with a random user id #12905
• docker images for APM Server failing with permission issues #18858
• Revert "Allow the Docker image to be run with a random user id (#12905)" #18872