Lazy load kernel sources

[DonJayamanne]

Fixes #11970

[codecov-commenter]

Codecov Report

Merging #11970 (77196a3) into main (0986b8f) will increase coverage by 1%.
The diff coverage is 0%.

❗ Current head 77196a3 differs from pull request most recent head 0b0fae3. Consider uploading reports for the commit 0b0fae3 to get more accurate results

@@           Coverage Diff           @@
##            main   #11970    +/-   ##
=======================================
+ Coverage     61%      62%    +1%     
=======================================
  Files        496      496            
  Lines      35205    35212     +7     
  Branches    5678     5679     +1     
=======================================
+ Hits       21607    22057   +450     
+ Misses     11581    11074   -507     
- Partials    2017     2081    +64     

Impacted Files	Coverage Δ
...llers/kernelSource/notebookKernelSourceSelector.ts	8% <0%> (-1%)	⬇️
src/kernels/raw/session/rawJupyterSession.node.ts	78% <0%> (-3%)	⬇️
src/notebooks/debugger/kernelDebugAdapterBase.ts	76% <0%> (-3%)	⬇️
src/kernels/helpers.ts	65% <0%> (-2%)	⬇️
src/platform/msrCrypto/msrCrypto.js	19% <0%> (-1%)	⬇️
src/kernels/installer/productInstaller.node.ts	78% <0%> (ø)
src/platform/common/utils/localize.ts	75% <0%> (+<1%)	⬆️
src/kernels/execution/helpers.ts	62% <0%> (+<1%)	⬆️
src/platform/common/utils.ts	79% <0%> (+<1%)	⬆️
src/notebooks/debugger/debuggerVariables.ts	67% <0%> (+1%)	⬆️
... and 41 more