Make the implementation declareModlueId safe to import and
execute in node.js, which does not provide a window global.

(N.B. because this is an ESM and therefore automatically
strict, using window?.goog?.declareModuleId doesn't work
because window being undefined is an early error.)

- Add a buildShims task to build_tasks.js that, for each chunk,
  creates a correspondingly-named build/<chunk>.mjs that will
  either (in uncompressed mode) import and reexport that chunk's
  entry point module (e.g. core/blockly.js) or (in compressed
  mode) load dist/<chunk>_compressed.js using a <script> tag
  and then export the corresponding properties on the chunk's
  exports object.

- Provide helper methods used by these shims in
  tests/scripts/loading.mjs, including code to detect whether
  to load in compressed or uncompressed mode.

- Add a quote() function to scripts/helpers.js, used by
  buildShims.  This is copied from tests/bootstrap_helper.js,
  which will be removed in a later commit.

…hims

Shared procedure support was moved to a plugin and this should
have been removed from core along with it.

Per suggestion on PR google#7380, have buildShims name the shims
${chunk.name}.loader.mjs instead of just `${chunk.name}.mjs`.