Use param serializer for synced URL parameters

[philippjfr]

Ensures parameter types other than the real basics can be synced with the Location components query parameters.

[codecov]

Codecov Report

Merging #1658 into master will increase coverage by 0.15%.
The diff coverage is 76.47%.

@@            Coverage Diff             @@
##           master    #1658      +/-   ##
==========================================
+ Coverage   85.10%   85.26%   +0.15%     
==========================================
  Files         148      148              
  Lines       16945    17107     +162     
==========================================
+ Hits        14421    14586     +165     
+ Misses       2524     2521       -3     

Impacted Files	Coverage Δ
panel/io/location.py	83.92% <76.47%> (-1.64%)	⬇️
panel/template/base.py	74.72% <0.00%> (-0.36%)	⬇️
panel/tests/test_template.py	98.18% <0.00%> (+0.65%)	⬆️
panel/layout/grid.py	81.45% <0.00%> (+6.45%)	⬆️
panel/depends.py	63.63% <0.00%> (+13.63%)	⬆️
panel/template/react/__init__.py	93.44% <0.00%> (+16.97%)	⬆️

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