feat: Update FileNameInput component with latest colors and design

[sehyod]

This updates the input for file names (when renaming) with the new semantic colors.
This adds all semantic colors as CSS variables
And this also removes old CSS and tailwind variables.
NB: The RewriteWidget component still uses some of the removed tailwind classes, but the component will be removed in #514

Screen.Recording.2023-09-11.at.10.53.32.mov

Closes #530

[codecov]

Codecov Report

Merging #531 (65d4e56) into main (39baccd) will increase coverage by 0.00%.
The diff coverage is 90.00%.

@@           Coverage Diff           @@
##             main     #531   +/-   ##
=======================================
  Coverage   81.81%   81.81%           
=======================================
  Files         218      218           
  Lines       12104    12105    +1     
  Branches     1197     1197           
=======================================
+ Hits         9903     9904    +1     
  Misses       2187     2187           
  Partials       14       14           

Files Changed	Coverage Δ
...otionBlock/plugins/collapsiblePlaceholderPlugin.ts	76.36% <0.00%> (ø)
src/components/FileNameInput.tsx	96.72% <100.00%> (+0.05%)	⬆️
src/features/ai/settings/OpenAiSettingsPane.tsx	100.00% <100.00%> (ø)
...or/components/tipTapNodes/citation/CitationNode.ts	100.00% <100.00%> (ø)
...pTapNodes/notionBlock/plugins/placeholderPlugin.ts	100.00% <100.00%> (ø)
...pTapNodes/sentenceCompletion/SentenceCompletion.ts	100.00% <100.00%> (ø)

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