refactor: Change ObjectSelector to Selector

[hoxbro]

See holoviz/param#728

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 69.30%. Comparing base (da8719e) to head (1eaed12).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
geoviews/operation/regrid.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #768      +/-   ##
==========================================
+ Coverage   67.40%   69.30%   +1.90%     
==========================================
  Files          45       45              
  Lines        4669     4721      +52     
==========================================
+ Hits         3147     3272     +125     
+ Misses       1522     1449      -73     

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