Replace inbuilt support for references with Param based references

[philippjfr]

Builds on holoviz/param#843 to replace existing support for Param references with internal support in Param. This has the major benefit that references can now be updated and that we allow for nested references.

[codecov]

Codecov Report

Merging #5530 (e4b5b81) into main (7088c68) will decrease coverage by 0.07%.
Report is 1 commits behind head on main.
The diff coverage is 98.03%.

@@            Coverage Diff             @@
##             main    #5530      +/-   ##
==========================================
- Coverage   83.59%   83.52%   -0.07%     
==========================================
  Files         277      277              
  Lines       40387    40269     -118     
==========================================
- Hits        33760    33636     -124     
- Misses       6627     6633       +6     

Flag	Coverage Δ
ui-tests	41.38% <81.37%> (-0.01%)	⬇️
unitexamples-tests	72.38% <98.03%> (-0.09%)	⬇️

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Files Changed	Coverage Δ
panel/pane/vega.py	82.10% <ø> (ø)
panel/depends.py	72.72% <50.00%> (+2.72%)	⬆️
panel/__init__.py	100.00% <100.00%> (ø)
panel/pane/base.py	84.53% <100.00%> (-1.30%)	⬇️
panel/pane/holoviews.py	79.28% <100.00%> (+0.03%)	⬆️
panel/pane/ipywidget.py	49.38% <100.00%> (-2.52%)	⬇️
panel/pane/markup.py	90.04% <100.00%> (ø)
panel/pane/perspective.py	68.30% <100.00%> (ø)
panel/pane/plot.py	68.83% <100.00%> (+0.27%)	⬆️
panel/pane/plotly.py	80.00% <100.00%> (ø)
... and 14 more

... and 10 files with indirect coverage changes

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