Split out -Wenum-explicit-default

enum's default is more problematic than the other types like
primitives/arrays.

By splitting them into separate warnings one may opt-in for
enum-explicit-default.

Bug: 175841271
Test: m aidl_unittests
Change-Id: I08c0f3cc4cb4a9973863e747cfe7e722a631016d
3 files changed