Add support for remote filesystems on FileSelector

[philippjfr]

Since #6837 requires some more work on the tree implementation but the remote file selection pieces are well supported this PR applies the changes from that PR minus the actual tree based components.

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 27 lines in your changes missing coverage. Please review.

Project coverage is 86.73%. Comparing base (6c9e955) to head (63dca20).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
panel/widgets/file_selector.py	84.56%	23 Missing ⚠️
panel/tests/widgets/test_file_selector.py	94.11%	2 Missing ⚠️
panel/compiler.py	0.00%	1 Missing ⚠️
panel/util/__init__.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7618      +/-   ##
==========================================
+ Coverage   86.19%   86.73%   +0.53%     
==========================================
  Files         341      341              
  Lines       51661    51764     +103     
==========================================
+ Hits        44530    44898     +368     
+ Misses       7131     6866     -265     

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