Automated tool for catching imports of missing components

There are some upstream components where we exclude all the files from moz.build:

protections/
pocket/
firefoxview/
pingsender/
extensions/formautofill
extensions/webcompat
extensions/pictureinpicture
extensions/search-detection
extensions/newtab
pbproxy
newtab/ as of #43886 (closed).

If any of the files registered under these directories is (lazy) loaded, then it will cause a console error and potentially short-circuit some code we need.

Therefore, it would be generally useful to have some means of detecting when upstream adds new code that tries to load one of these missing components, rather than having to do this manually.

In particular, if we follow rapid release these problems will arise at different times.

I know of at least two upcoming upstream changes that will effect us:

Bugzilla bug 1973104 landed in 142, which adds a new path for a newtab component.
Buzilla bug 1877695 landed in 141, which adds a new path for the protections component.

@brizental do you know whether this is covered by a linter that takes moz.build into account? If not, is there a linter we could modify to do this?

Otherwise, should we create our own script?

/cc @pierov @morgan

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