chore(deps): upgrade to webpack v5 (#4073)

this commit updates stencil version of webpack to v5. webpack is used in
stencil for the purpose of bundling external dependencies (said deps can
be found in `scripts/bundles/sys-node-bundle-cache` after a build).

in order to perform the migration the steps contained in
https://webpack.js.org/migrate/5/ were followed. specifically:
- old typings were removed
- the webpack configuration was un-lined to validate the types of the
  object
- old node types, `process` and `Buffer` were removed, as they are no
  longer supported in v5 (and were unused to start with)
- checks against the `request` object being falsy in the `externals`
  function were added