This commit removes the testability features that are internal only.
This simplifies the implementation of testability which will need
updates to support zoneless. Those updates will be easier to manage if
the Testability implementation is simpler.
While protractor is indeed officially EOL, we will still need to do some
updates to support teams migrating to zoneless that have protractor
tests.
As far as protractor's own use of `whenStable`, it does not read the
internal only methods either:
https://github.com/angular/protractor/blob/master/lib/clientsidescripts.js
Anything else depending on these values are not following the defined public API
contract.
PR Close#53767
