[www][UI] bug fixes | enhancements

[sahirgomez1]

This PR fixes:

• Loading indicator for sluggish environments, when making api calls.
• Fixes bug : root node unresponsive -
• Fixes dark mode in UI components
• Adds detection of system theme to update theme interface programmatically.
• Renames "CompilerGym" to "CompilerGym Explorer" in the top left navbar.
• Removes unused links in main navbar.
• Fixes bug: message "copied to clipboard" not updating on closing share modal.

Ref: https://docs.google.com/document/d/1HRZEsHPfHey769x1vTR8ZJ1ef5ks0AADmHpxYrEgJkc/edit

https://user-images.githubusercontent.com/84393628/187105573-71ee225b-73e6-4546-a7a3-c1c5e061e3f7.mov

https://user-images.githubusercontent.com/84393628/187106148-0912a620-1b07-4f21-a305-c1908a89e779.mov

[codecov-commenter]

Codecov Report

Merging #763 (6b22108) into development (1c40e5b) will decrease coverage by 33.75%. The diff coverage is n/a.

@@               Coverage Diff                @@
##           development     #763       +/-   ##
================================================
- Coverage        89.29%   55.53%   -33.76%     
================================================
  Files              130      130               
  Lines             7912     7912               
================================================
- Hits              7065     4394     -2671     
- Misses             847     3518     +2671     

Impacted Files	Coverage Δ
compiler_gym/util/permutation.py	0.00% <0.00%> (-100.00%)	:arrow_down:
compiler_gym/leaderboard/__init__.py	0.00% <0.00%> (-100.00%)	:arrow_down:
compiler_gym/service/runtime/__init__.py	0.00% <0.00%> (-100.00%)	:arrow_down:
compiler_gym/service/runtime/benchmark_cache.py	0.00% <0.00%> (-100.00%)	:arrow_down:
...mpiler_gym/service/runtime/compiler_gym_service.py	0.00% <0.00%> (-100.00%)	:arrow_down:
...ice/runtime/create_and_run_compiler_gym_service.py	0.00% <0.00%> (-100.00%)	:arrow_down:
compiler_gym/envs/gcc/service/gcc_service.py	0.00% <0.00%> (-95.98%)	:arrow_down:
compiler_gym/leaderboard/llvm_instcount.py	0.00% <0.00%> (-92.79%)	:arrow_down:
compiler_gym/util/minimize_trajectory.py	0.00% <0.00%> (-92.63%)	:arrow_down:
...loop_tool/service/loop_tool_compilation_session.py	0.00% <0.00%> (-91.22%)	:arrow_down:
... and 78 more