[WIP] build: use a bundler (esbuild) along with vsce to package vsix files

[mohanraj-r]

What does this PR do?

Uses esbuild to bundle (and treeshake) JS files before packaging them into vsix with vsce. This would lead to

• significant reduction in file sizes leading to faster downloading and potentially faster loading of extensions for users
• breaking dependence on npm v6 for vsce package which is currently blocking us from upgrading to npm v7/v8 (node 16) or pnpm
• Continues chore: first try with esbuild to reduce extension size @W-6980161@ - WIP #3748

What issues does this PR fix or reference?

@W-6980161@

Functionality Before

• vsce package was used to produce vsix files

Functionality After

• vsce package is used along with esbuild to produce vsix files

Notes

• Currently npm prune --production is run before vsce package
  • This removes all dev dependencies
    • Hence current packaging is a destructive operation requiring install and compile to continue develop
  • vsce package then gets a list of files to be packaged from the package manager (auto-detected)
  • Without npm prune, vsce packaging errors complaining about the dev deps e.g. with npm ERR! extraneous: [email protected]
    • Even using a tool such as duniul/clean-modules: 🧹 Clean up/prune unnecessary files and reduce the size of your node_modules directory. in place of npm prune doesn't work

Future considerations 👉

• QA
  • Even when bundling isn't working correctly (missing to identify files to bundle due to dynamic imports e.g.) the vsix files build and install without any errors
    • Have to watch for extension activation errors in VSCode dev console, ext host log etc
    • Without automated e2e tests to verify correct activation and e2e functionality of the extensions, bundling could risk the quality of the releases
• Debugging / user error reporting
  • Stack traces become harder to read and less informative with bundled packages