Use TetheredInterfaceRequester to check available tethering interface

Used for deciding what test needs to be run. Moreover, the
EthernetManager#isAvailable is not used for this purpose
anymore. The restricted networks permission is not required
as well.

Bug: 237369591
Bug: 242067530
Test: atest EthernetTetheringTest
Change-Id: I1215278271ca6b48e097d7f2cf160416d54116f2
1 file changed