init: remove unneeded special cases from FscryptInferAction

All the individual directories being treated specially by
FscryptInferAction() already have an explicit encryption action in the
corresponding mkdir commands.  The explicit action is the source of
truth, so the special cases in FscryptInferAction() are unnecessary.

Also, some of these cases were outdated.  For example, /data/app-staging
was changed from encryption=None to encryption=DeleteIfNecessary at some
point, but FscryptInferAction() was not updated.  This is causing the
warning "Inferred action different from explicit one" to be logged.

Additional "Inferred action different from explicit one" warnings are
logged due to subdirectories of /data/apex being explicitly encrypted.

Change FscryptInferAction() to only do what it needs to do: check
whether the directory is a top-level directory of /data or not.  Remove
the above-mentioned warning which is not useful.

Bug: 232554803
Change-Id: If6611d64107a19d242892c92dfea095577e193e5