New integration test for fs-verity install and on-access verification

There are two categories of tests:

1. Package installation with .fsv_sig
  * .apk, .dm, including the split ones should all or none be installed
     with their corresponding .fsv_sig files

2. End-to-end fs-verity test of on-access verification
  * When fs-verity is enabled to a file, if the on-disk content is
    changed, the read should fail.

See class comment in ApkVerityTest.java for the test details.

Brief directory layout overview:
* src/
  - Actual test
* ApkVerityTestApp/
  - Dummy app for testing, including a split
* testdata/
  - Some artifacts, signing key and fs-verity signatures
* block_device_writer/
  - Helper binary for write a file directly on disk

Test: atest
Bug: 112039386
Change-Id: I3b8229037db682f36fda9d5cafd14caf6b39501d