Limit number of times we enter the darks state

[danjampro]

Adds new should_take_darks property to the HuntsmanPOCS class.

New config items: calibs.dark.max_blocks_per_interval: The maximum number of times to enter the state. calibs.dark.dark_interval_hours: The time interval in which the maximum number pertains.

Each time the dark state is completed, the time is registered inside the HuntsmanPOCS instance. If there have been too many darks collected recently (defined by the new config items) then the dark state will be vetoed.

Closes #527

[codecov[bot]]

Codecov Report

Merging #530 (256dfb8) into develop (404bedb) will decrease coverage by 0.01%. The diff coverage is 59.25%.

:exclamation: Current head 256dfb8 differs from pull request most recent head 2e87a15. Consider uploading reports for the commit 2e87a15 to get more accurate results

@@             Coverage Diff             @@
##           develop     #530      +/-   ##
===========================================
- Coverage    55.89%   55.88%   -0.02%     
===========================================
  Files           62       62              
  Lines         4011     4037      +26     
  Branches       432      436       +4     
===========================================
+ Hits          2242     2256      +14     
- Misses        1656     1665       +9     
- Partials       113      116       +3     

Impacted Files	Coverage Δ
src/huntsman/pocs/states/huntsman/starting.py	0.00% <0.00%> (ø)
src/huntsman/pocs/states/huntsman/taking_darks.py	0.00% <0.00%> (ø)
src/huntsman/pocs/core.py	61.17% <64.00%> (+1.17%)	:arrow_up:
src/huntsman/pocs/archive/archiver.py	88.28% <0.00%> (-1.81%)	:arrow_down:

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