Allow partially unsyncing parameterized from the Location

[philippjfr]

Previous unsync would always operate on all the parameters of a Parameterized, now you can partially unsync just a subset of parameters.

• Fixes Please add functionality to change the parameters to sync via the Location component #1335
• Add tests

[codecov]

Codecov Report

Merging #1532 into master will increase coverage by 0.01%.
The diff coverage is 95.65%.

@@            Coverage Diff             @@
##           master    #1532      +/-   ##
==========================================
+ Coverage   85.72%   85.73%   +0.01%     
==========================================
  Files         145      145              
  Lines       15996    16015      +19     
==========================================
+ Hits        13713    13731      +18     
- Misses       2283     2284       +1     

Impacted Files	Coverage Δ
panel/io/location.py	81.44% <91.66%> (+0.54%)	⬆️
panel/tests/io/test_location.py	100.00% <100.00%> (ø)

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