AssetManager2: Fix list function

List was skipping directories. Include them, and add tests to ensure
the order and precedence is correct.

Bug: 72511641
Test: make libandroidfw_tests
Test: atest CtsContentTestCases:AssetManagerTest
Change-Id: Iadf45883283d3e4aae93bd7c3343745912e34fa0
13 files changed