feat: add start and stop writing top level commands

[shihab-dls]

Closes #75

This PR currently just adds top level start_writing and stop_writing commands, using _filter_sub_controllers and some cached_property's.

This will be rebased over ControllerVector changes in FastCS, and amended, before merging.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.76%. Comparing base (b508374) to head (441feb2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
+ Coverage   88.15%   88.76%   +0.60%     
==========================================
  Files          14       14              
  Lines         574      605      +31     
==========================================
+ Hits          506      537      +31     
  Misses         68       68              

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[GDYendell]

This looks good.