enh(dev): Migrate from webpack to vite for building the frontend

[susnux]

Using vite over webpack has some benefits like better treeshaking and faster compile times (due to use of esbuild vs terser). So for forms this means:

build	script size (du -bs js) without source maps
webpack	8939919 B
vite	2315149 B

This can not be backported because module JS is only supported since Nextcloud 27.

[codecov]

Codecov Report

Merging #1827 (f228767) into main (7a147d9) will increase coverage by 0.19%.
Report is 23 commits behind head on main.
The diff coverage is 0.00%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1827      +/-   ##
============================================
+ Coverage     43.96%   44.15%   +0.19%     
  Complexity      646      646              
============================================
  Files            58       58              
  Lines          2550     2539      -11     
============================================
  Hits           1121     1121              
+ Misses         1429     1418      -11