Rename Path.iterator method to avoid AndroidX collision

There will be an extension function in the AndroidX version
of this API with the name 'iterator'. Callers of that API
should get the extension version instead, but Kotlin defers
to the actual implementation if it exists. Changing the method
name here (and removing the new implementation of the
Iterable interface) to avoid that collision.

Bug: 223586753
Test: Changed PathIterator cts tests to suit

Change-Id: I30e2c227ddc4fd387a90d72c52c1324c9207a3a7