Refactor CI to handle skipping docs

[jtoar]

Closes #4848.

This refactors our GitHub workflows so that our CI passes required checks for PRs with docs-only changes.
It also tweaks the names of the jobs a bit (i.e., adding emojis) to make things a little easier to read at a glance. @thedavidprice We may have to update the names of the required checks accordingly.

To do all this, I merged the build-eslint-jest, e2e, and smoke-test workflows into one file—ci—so I could "route" the jobs based on the files changed by a PR. But I made no changes to the workflows themselves (i.e. they still check for the same things):

Here's the routing for a regular PR that includes code changes:

Step by step, here's what happens:

• The "Only docs changes" job runs, figures out if ONLY docs changed (see below)
• If more than just docs changed, the "Check" job runs, which runs yarn check, making sure the basics look ok before launching an onslaught of jobs
• If check passes, 10 jobs are triggered:
  • Build, lint, test x 4
  • Tutorial e2e x 2
  • Smoke test x 4

A docs-only PR would just run echo pass for everything, passing instantly.

You can see this workflow in action now, on this PR and in the Checks tab and on this page below:

(Here's what it looked like before for reference)

---

Lastly, here's the files that this action considers docs:

redwood/.github/actions/only_doc_changes/only_doc_changes.mjs

Lines 10 to 27 in de0f6f6

	for (const changedFile of changedFiles) {
	if (changedFile.startsWith('docs')) {
	continue
	}
	for (const fileToIgnore of [
	'CHANGELOG.md',
	'CODE_OF_CONDUCT.md',
	'CONTRIBUTING.md',
	'CONTRIBUTORS.md',
	'LICENSE',
	'README.md',
	'SECURITY.md',
	]) {
	if (changedFile === fileToIgnore) {
	continue
	}
	}

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[thedavidprice]

Looking good! I think I'll need to walk through this one with you in real-time. Possible?