feat!(rsyncd): add `sshd` as an alternative Rsync Daemon to `rsyncd`

[dduportal]

Related to https://github.com/jenkins-infra/helpdesk/issues/4402

This PR adds the support of an alternative rsync backend: sshd in the rsyncd chart.

It introduces a set for changes, which most of them are breaking and requires values updates:

• BREAKING CHANGE: the default user changes from nobody:nogroup (65534:65534) to rsyncd:rsyncd (1000:1000)
• BREAKING CHANGE: Default user dir changes from /nowhere to /home/rsyncd
• BREAKING CHANGE: Default run temp dir for PID files changes from /run to /home/rsyncd/run
• BREAKING CHANGE: All rsync directories (when using rsyncd) directories (data/, /etc) changes to /home/rsyncd/*
• Enhancement: allows to use sshd instead of rsyncd, configured by the new value configuration.rsyncd_daemon set to sshd. Otherwise defaults to rsyncd. When enabled:
  • Internally exposed port (pod) changes from 1873 to 2222 (unless specified through the value port)
  • Service exposed port changes from 873 to 22 (unless specified through the value service.port)
  • Bumps the container image to 2.1.0 (ref. https://github.com/jenkins-infra/docker-rsyncd/compare/1.0.68...2.1.0)
  • The public key for the user rsyncd can be specified using the value configuration.sshd.public_key
  • The sshd daemon log level can be set up through the value configuration.sshd.log_level (defaults to INFO)
• BREAKING CHANGE: deprecate usage of the MotD. The value configuration.motd is now ignored
• Enhancement: data volumes specified by the configuration.components directive may have writing enabled with the new attribute writeEnabled