🏗✨ Upgrade to Babel 7

[rsimha]

It's been a year since we upgraded to Babel 6 in #9775. It's time to upgrade to Babel 7.

Things this PR does:

1. Replaces babel-core (version 6) with @babel/core (version 7, from the new babel monorepo)
2. Updates all other babel packages with their latest monorepo equivalents
3. Updates babelify from version 8 (compatible with babel 6) to version 10 (compatible with babel 7)
4. Moves configurations from .babelrc to babel.config.js
5. Consolidates all the different babelify settings across the codebase into babel.config.js (Fixes Centralize browserify config #18582)
6. Consolidates build-system/tasks/compile-{access|bind|css}-expr.js into a single file compile-expr.js (and removes the _token-stack: label from the generated jison parser in order to satisfy babel 7)
7. Removes the global: true setting for babelify added in Upgrade Closure Compiler to v20171112 #18552 (so that node_modules dependencies are also compiled) and replaces it with a less risky method that does a babelify transform for only those node_modules packages that we ship with the runtime
8. Eliminates the use of the babel-plugin-transform-remove-strict-mode package that was added during the babel 6 upgrade in upgrade to babel 6 #9775 to prevent use strict errors, and enables strict mode during development
9. Fixes instances where code was incorrectly writing to read-only properties, now that strict mode is enabled and enforced during development and unit testing

With this, all traces of babel 6 should be gone from our code-base, and babel 7 should be the only means of compiling unminified code.

Fixes #18654
Fixes #18582
Closes #18199

[rsimha]

@erwinmombay @jridgewell @kristoferbaxter @choumx I'm sending this out for preliminary high level comments while I continue to work on it.

As things stand right now, gulp build and gulp serve work with babel 7. I can get all example pages to load correctly. Still working on some test failures.

[rsimha]

This is now ready for review.

[jridgewell]

I'm very worried about performance regressions that'll be caused by this. The token-stack appears to create a lot of arrays and array mutations.

Is this still needed? If the _token_stack label still needs to be stripped, can we do it as a post-process step instead of changing the JISON algorithm?

[rsimha]

Compiling with babel 7 fails without this. I found this fix in the jison codebase. Do you have a suggestion for a better way to strip this label?

[rsimha]

@jridgewell WDYT?

[kristoferbaxter]

One item I believe you should address here, left a few comments.

[rsimha]

All comments addressed. PTAL.

[rsimha]

@kristoferbaxter I hesitate to make extensive changes to compile-expr.js in this PR (since I'm merely moving code around here to ease the babel upgrade). Okay if we deal with these in a follow up PR? (I'll be sure to have you review it.)

[kristoferbaxter]

Left a few comments on the compile-expr file.

[kristoferbaxter]

Happy to have a followup PR for compile-expr. Nice work!

[rsimha]

@jridgewell Comments addressed. PTAL.

[rsimha]

Merged!

https://www.youtube.com/watch?v=40abpedBKK8