* Fix ESLint crash on empty react effect hook

* Add layout effect to test

* Improve wording in comment

* Improve lint warning wording

* Reword missing effect callback message

The goal is to simplify our CI pipeline so that all configurations
are built and tested in a single workflow.

As a first step, this adds a new build script entry point that builds
both the experimental and stable release channels into a single
artifacts directory.

The script works by wrapping the existing build script (which only
builds a single release channel at a time), then post-processing the
results to match the desired filesystem layout. A future version of the
build script would output the files directly without post-processing.

Because many parts of our infra depend on the existing layout of the
build artifacts directory, I have left the old workflows untouched.
We can incremental migrate to the new layout, then delete the old
workflows after we've finished.

Fixes issue in the new build workflow where the experimental packages do
not include "experimental" in the version string. This was because the
previous approach relied on the RELEASE_CHANNEL environment variable,
which we are no longer setting in the outer CI job, since we use the
same job to build both channels. To solve, I moved the version
post-processing into the build script itself.

Only affects the new build workflow. Old workflow is unchanged.

Longer term, I would like to remove version numbers from the source
entirely, including the package.jsons. We should use a placeholder
instead; that's mostly how it already works, since the release script
swaps out the versions before we publish to stable.

Currently, if publishing a package fails, the script crashes, and the
user must start it again from the beginning. Usually this happens
because the one-time password has timed out.

With this change, the user will be prompted for a fresh otp, and the
script will resume publishing.

* Test: Deletion effects should fire parent -> child

Regression in new effect implementation

* Fix passive deletion effect ordering

We need to call `detachFiberAfterEffects` on the fiber's alternate to
clean it up. We're currently not, because the `alternate` field is
cleared during `detachFiberMutation`. So I deferred detaching the
`alternate` until the passive phase. Only the `return` pointer needs to
be detached for semantic purposes.

I don't think there's any good way to test this without using
reflection. It's not even observable using out our "supported"
reflection APIs (`findDOMNode`), or at least not that I can think of.
Which is a good thing, in a way.

It's not really a memory leak, either, because the only reference to the
alternate fiber is from the parent's alternate. Which will be
disconnected the next time the parent is updated or deleted.

It's really only observable if you mess around with internals in ways
you're not supposed to — I found it because a product test in www that
uses Enzyme was doing just that.

In lieu of a new unit test, I confirmed this patch fixes the broken
product test.

* Migrate prepare-release-from-ci to new workflow

I added a `--releaseChannel (-r)` argument to script. You must choose
either "stable" or "experimental", because every build job now includes
both channels.

The prepare-release-from-npm script is unchanged since those releases
are downloaded from npm, nt CI.

(As a side note, I think we should start preparing semver releases using
the prepare-release-from-ci script, too, and get rid of
prepare-release-from-npm. I think that was a neat idea originally but
because we already run `npm pack` before storing the artifacts in CI,
there's really not much additional safety; the only safeguard it adds is
the requirement that a "next" release must have already been published.)

* Move validation to parse-params module

…se cache usage