Simplify findSolid and findFace

[RubenRubens]

These are breaking changes. I believe they are worth considering thought. Few users would be affected and makes cq code much cleaner. For example, both Fx Bricks and Paramak have 0 references to findSolid.

[codecov]

Codecov Report

Merging #662 (ae13a84) into master (e4ed881) will increase coverage by 0.00%.
The diff coverage is 93.75%.

@@           Coverage Diff           @@
##           master     #662   +/-   ##
=======================================
  Coverage   94.03%   94.03%           
=======================================
  Files          31       31           
  Lines        6636     6637    +1     
  Branches      726      726           
=======================================
+ Hits         6240     6241    +1     
  Misses        258      258           
  Partials      138      138           

Impacted Files	Coverage Δ
cadquery/cq.py	89.90% <93.75%> (+0.01%)	⬆️
cadquery/occ_impl/shapes.py	91.89% <0.00%> (ø)

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[marcus7070]

Ok, so you've simplified findSolid to two use cases:

1. search stack and parents
2. do not search stack but search parents

Instead of the string argument, can we just keep the searchStack bool argument and drop the searchParents?

I agree with the simplification, I've never used findSolid(searchParents=False), and if I ever needed to do that job I think I'd use a more general python technique like next(x for x in wp.vals() if isinstance(x, cq.Solid)).

I'm about to change the behaviour of findSolid in #662 #655 anyway, so good timing for this.

[RubenRubens]

This might not be that interesting after all. So, don't waste time in here. I might consider reopening this PR soon with some interesting ideas. :)