Several perf problems with the build that need to be addressed:

• All agents do the same compilation/optimization/minification
• Each extension get compiled/optimized/webpacked 6 (!) times
• node.exe gets downloaded 2 times
• macOS agents seem slower than before, though they end up doing more than others:
  • Sourcemaps
  • Bundle stats (Submitted bundle stats)

DONE ✔️

• Remove VSCODE_WEB hack, create vscode-web-* tasks
• De-duplicate compilation tasks
  • Remove old extensions compilation
  • Dedupe extensions build
  • Cleanup Node.JS downloading
  • Dedupe Node.JS downloading
  • Dedupe vscode build
    • Alpine
    • ARM
• Verify Webpack catches TS type errors
• Use the Yarn cache task
• Run common steps only once in a separate Linux build agent
  • Hygiene
  • Compilation
  • Optimization & minification
  • Cache result in VSTS artifacts, such that other agents and successive build resubmissions can simply pick that up
• Have VSCODE_COMPILE_ONLY flag
• Get template for arm/alpine
• Remove node build/lib/builtInExtensions.js
• Move quality/*/package.json dependencies into actual package.json dependencies
• Deduplicate extension compilation Remove legacy extensions compilation from build #77058
• Cleanup VSCODE_ARCH usages in Linux build 7b0cd32
• Set sensible values for task timeout
• Lower agent parallel jobs
• Move sourcemaps to common agent
• Move bundle stats to common agent
• Move upload-configuration to common agent