Share runBp2BuildTestCase & runPythonTestCase

Pull along bp2buildTestCase as well
Because none are specific to their current hosts

Move `errored` up to the "generic" block vs.
the "custom" block

Test: Existing tests pass
Change-Id: Ie8d5322a5554ebd88f0c142a4c541791687be326

bp2build/python_binary_conversion_test.go

@@ -3,15 +3,9 @@ package bp2build
 import (
 	"testing"
 
-	"android/soong/android"
 	"android/soong/python"
 )
 
-func runPythonTestCase(t *testing.T, tc bp2buildTestCase) {
-	t.Helper()
-	runBp2BuildTestCase(t, func(ctx android.RegistrationContext) {}, tc)
-}
-
 func TestPythonBinaryHostSimple(t *testing.T) {
 	runPythonTestCase(t, bp2buildTestCase{
 		description:                        "simple python_binary_host converts to a native py_binary",