clean up interactive window creation

[amunger]

Part of #10808

• Remove the excessive thread safety, the deferred creation promise should be enough to ensure duplicate IWs are not created
• Stop subscribing to events each time a cell is added by making the restore method more idempotent

[codecov-commenter]

Codecov Report

Merging #11544 (77afeda) into main (48fa7d5) will decrease coverage by 0%.
The diff coverage is 100%.

❗ Current head 77afeda differs from pull request most recent head d281721. Consider uploading reports for the commit d281721 to get more accurate results

@@          Coverage Diff           @@
##            main   #11544   +/-   ##
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- Coverage     63%      63%   -1%     
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  Files        477      477           
  Lines      34133    34070   -63     
  Branches    5540     5529   -11     
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- Hits       21567    21501   -66     
  Misses     10505    10505           
- Partials    2061     2064    +3     

Impacted Files	Coverage Δ
...teractive-window/editor-integration/codewatcher.ts	70% <ø> (-1%)	⬇️
src/interactive-window/types.ts	100% <ø> (ø)
src/interactive-window/interactiveWindow.ts	75% <100%> (+<1%)	⬆️
...rc/interactive-window/interactiveWindowProvider.ts	76% <100%> (-1%)	⬇️
src/kernels/execution/notebookUpdater.ts	88% <0%> (-8%)	⬇️
src/kernels/installer/productInstaller.node.ts	74% <0%> (-7%)	⬇️
src/kernels/helpers.node.ts	62% <0%> (-5%)	⬇️
...rc/platform/common/application/applicationShell.ts	24% <0%> (-4%)	⬇️
src/notebooks/controllers/kernelRanking/helpers.ts	58% <0%> (-2%)	⬇️
src/kernels/jupyter/jupyterKernelService.node.ts	72% <0%> (-2%)	⬇️
... and 25 more

[rebornix]

Reading pendingCreation, it gave me a feeling that we can have multiple creation in parallel. However we are awaiting for all pending creations to be complete before creating new ones, does it mean that pendingCreation.length <= 1 always? If so we can probably change it to pendingCreations: Promise<void> | null

[amunger]

yeah I noticed that as well, I'll change it to better express that only one creation is happening at a time

[rebornix]

Looks good to me in overall. Only nick pick of how we manage pendingCreation