feat(unit): allow to start/stop timers

[msciciel]

PR progress checklist (to be filled in by reviewers)

• Changes to documentation are appropriate (or tick if not required)
• Changes to tests are appropriate (or tick if not required)
• Reviews completed

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What type of PR is this?

Primary type

• [build] Changes related to the build system
• [chore] Changes to the build process or auxiliary tools and libraries such as documentation generation
• [ci] Changes to the continuous integration configuration
• [feat] A new feature
• [fix] A bug fix
• [perf] A code change that improves performance
• [refactor] A code change that neither fixes a bug nor adds a feature
• [revert] A change used to revert a previous commit
• [style] Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc.)

Secondary type

• [docs] Documentation changes
• [test] Adding missing or correcting existing tests

Does this PR introduce a BREAKING CHANGE?

No.

Related issues and/or pull requests

Describe the changes you're proposing

Allow to start/stop unit files of type timer.

Pillar / config required to test the proposed changes

systemd:
  timer:
    example:
      status: start
      Unit:
        Description: example
      Timer:
        Unit: example.service
        OnCalendar: "00:01:00"
      Install:
        WantedBy: timers.target

Debug log showing how the proposed changes work

[INFO    ] Running state [systemctl start example.timer] at time 13:48:45.541455
[INFO    ] Executing state cmd.wait for [systemctl start example.timer]
[INFO    ] No changes made for systemctl start example.timer
[INFO    ] Completed state [systemctl start example.timer] at time 13:48:45.553760 (duration_in_ms=12.305)

Documentation checklist

• Updated the README (e.g. Available states).
• Updated pillar.example.

Testing checklist

• Included in Kitchen (i.e. under state_top).
• Covered by new/existing tests (e.g. InSpec, Serverspec, etc.).
• Updated the relevant test pillar.

Additional context