No matter how microdroid system's sepolicy is built, microdroid vendor's
sepolicy will exist under packages/modules/Virtualization/microdroid,
and we need to trim vendor sepolicy first, to investigate further.

This commit removes almost all of vendor sepolicy files. Only the
keymint HAL and file_contexts stay.

Bug: 191131624
Test: atest MicordroidHostTestCases
Change-Id: Ib67507c1893d7768d2214c2bfbf2eaf299fb21f2