Organize Soong's integration tests:

- Move them into a new directory
- Split tests by theme and add a library file
- Add a shell script that runs them all

Test: Manually ran build/soong/run_integration_tests.sh .
Change-Id: I758b91d679f41aee47d15472cc02547ce89f6386
diff --git a/tests/run_integration_tests.sh b/tests/run_integration_tests.sh
new file mode 100755
index 0000000..db24037
--- /dev/null
+++ b/tests/run_integration_tests.sh
@@ -0,0 +1,6 @@
+#!/bin/bash
+
+TOP="$(readlink -f "$(dirname "$0")"/../../..)"
+"$TOP/build/soong/tests/bootstrap_test.sh"
+"$TOP/build/soong/tests/mixed_mode_test.sh"
+