Update variable wait to allow for triggering on any update

[slacrherbst]

This adds an update flag to the local VariableValue class used in the variable wait lambda function. This allows VariableWait to stall on an update of a variable without caring about a particular value. This is useful for variables which are updated on data reception.

This also updates the incorrect documentation and code comments.

The Advance function is removed from the Process class and the default example loop updates are fixed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 30.04%. Comparing base (04d1e8a) to head (30e158f).
Report is 13 commits behind head on pre-release.

Files	Patch %	Lines
python/pyrogue/_Process.py	0.00%	2 Missing ⚠️
python/pyrogue/_Variable.py	0.00%	2 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff              @@
##           pre-release     #994   +/-   ##
============================================
  Coverage        30.04%   30.04%           
============================================
  Files               65       65           
  Lines             6644     6644           
  Branches          1015     1015           
============================================
  Hits              1996     1996           
  Misses            4491     4491           
  Partials           157      157           

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