Move ds web pack scripts into build/webpack folder

[DonJayamanne]

Part of #9055
(next PR is #9373 where #9055 is resolved)

[codecov-io]

Codecov Report

Merging #9369 into master will decrease coverage by 1.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #9369      +/-   ##
==========================================
- Coverage   60.33%   59.21%   -1.12%     
==========================================
  Files         545      550       +5     
  Lines       28668    30046    +1378     
  Branches     4345     4683     +338     
==========================================
+ Hits        17296    17792     +496     
- Misses      10436    11285     +849     
- Partials      936      969      +33

Impacted Files	Coverage Δ
...ascience/jupyter/liveshare/guestJupyterNotebook.ts	7.05% <0%> (-3.43%)	⬇️
...atascience/interactive-window/interactiveWindow.ts	17.31% <0%> (-1.69%)	⬇️
src/client/datascience/jupyter/jupyterNotebook.ts	3.73% <0%> (-1.1%)	⬇️
src/client/datascience/serviceRegistry.ts	0% <0%> (ø)	⬆️
src/client/datascience/types.ts	100% <0%> (ø)	⬆️
...ient/datascience/jupyter/kernels/kernelSwitcher.ts	83.82% <0%> (ø)
src/client/datascience/commands/commandRegistry.ts	28.15% <0%> (ø)
src/client/datascience/commands/kernelSwitcher.ts	91.66% <0%> (ø)
src/client/datascience/commands/serverSelector.ts	81.81% <0%> (ø)
src/client/datascience/jupyter/serverSelector.ts	91.83% <0%> (ø)
... and 5 more

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[IanMatthewHuff]