gsi_util: adding check_compat subcommand

'check_compat' command can check the compatibility between
system and vendor image, which can be any source supported by
mounters, ex. image file, folder or adb.

Uses following command for the detail:

    $ ./gsu_util.py check_compat --help

The patch also includes a 'checker' framework. There is only
one checker 'VintfChecker' at this time. VintfChecker uses a
host tool, 'checkvintf', to check the compatibility.

Bug: 70253825
Test: check_compat with different mounters
Change-Id: I459b4cbd38465c0058087b4c68bca66e491c940e
diff --git a/gsi/gsi_util/Android.bp b/gsi/gsi_util/Android.bp
index cf72dd9..c1b2828 100644
--- a/gsi/gsi_util/Android.bp
+++ b/gsi/gsi_util/Android.bp
@@ -17,6 +17,7 @@
   srcs: [
     "gsi_util.py",
     "gsi_util/*.py",
+    "gsi_util/checkers/*.py",
     "gsi_util/commands/*.py",
     "gsi_util/dumpers/*.py",
     "gsi_util/mounters/*.py",
@@ -25,6 +26,7 @@
   required: [
     "adb",
     "avbtool",
+    "checkvintf",
     "simg2img",
   ],
   version: {