Refactor ScopedStorageTest to run on any volume

Add mechanism to run ScopedStorageTest test cases on different volumes,
and not necessarily the main volume.

Also add a TEST_MAPPING file.

Test: atest CtsScopedStorageHostTest
Bug: 148841336
Change-Id: I8e2eb0f14e10dbe5dcf4d5e12d9ac4f44ed1c2ee
4 files changed