Update gallery to use panel-material-ui

[philippjfr]

Updates all gallery examples to use panel-material-ui and makes panel-material-ui a required dependency.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.75%. Comparing base (8489abc) to head (4bf7cb8).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8596      +/-   ##
==========================================
- Coverage   85.77%   85.75%   -0.03%     
==========================================
  Files         350      350              
  Lines       56820    56820              
==========================================
- Hits        48738    48724      -14     
- Misses       8082     8096      +14     

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