Fix optimize_projection handling in YAML parsing

[djhoese]

Broken in #577. I accidentally stopped passing/parsing optimize_projection to DynamicAreaDefiniton objects parsed from YAML. This was first noticed in Satpy's tests. This PR fixes it. As stated in #577, I'd still like to follow this up with a PR to move metadata from YAML being any random kwarg to being an explicit attrs key.

• Closes #xxxx
• Tests added
• Tests passed
• Passes git diff origin/main **/*py | flake8 --diff
• Fully documented

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9c94b08) 93.99% compared to head (4dfcda6) 94.00%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #585   +/-   ##
=======================================
  Coverage   93.99%   94.00%           
=======================================
  Files          92       92           
  Lines       13777    13785    +8     
=======================================
+ Hits        12950    12958    +8     
  Misses        827      827           

Flag	Coverage Δ
unittests	94.00% <100.00%> (+<0.01%)	⬆️

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[coveralls]

coverage: 93.66% (+0.004%) from 93.656%
when pulling 4dfcda6 on djhoese:bugfix-opt-proj-yaml
into 56da958 on pytroll:main.