Move AVF tests to avf-pre/postsubmit test group

AVF presubmit test config currently runs all tests in the 'presubmit'
group. However, in presubmit the test configs are invoked with all
TEST_MAPPING paths from all affected CLs. Our test config can therefore
run tests from TEST_MAPPINGs outside of the Virtualization repo.

To work around this problem, move all Virtualization tests to
'avf-presubmit' group. Test config running in presubmit will still be
invoked with TEST_MAPPINGs from various repos but only our tests will
match the group.

Rename the postsubmit group to 'avf-postsubmit' for consistency.

Bug: 236755822
Test: atest --test-mapping packages/modules/Virtualization:avf-presubmit
Test: atest --test-mapping packages/modules/Virtualization:avf-postsubmit
Change-Id: I7be5781bef4b6e060a69724c7b4256423adc649c
diff --git a/TEST_MAPPING b/TEST_MAPPING
index e42533d..11648c4 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -1,5 +1,5 @@
 {
-  "presubmit": [
+  "avf-presubmit": [
     {
       "name": "MicrodroidHostTestCases"
     },
@@ -19,7 +19,7 @@
       "name": "compos_key_tests"
     }
   ],
-  "postsubmit": [
+  "avf-postsubmit": [
     {
       "name": "odsign_e2e_tests_full"
     },