Use one mutator for all bp2build conversion.

Each conversion required defining a separate mutator, which will each
operate on _all_ modules and requires each to repeat checks whether the
mutator should operator. Instead, we introduce a single mutator and
modules can define a ConvertWithBp2build to implement bp2build
conversion for that module.

Test: bp2build.sh
Bug: 183079158
Change-Id: I99d4b51f441c2903879092c5b56313d606d4338d
diff --git a/bp2build/android_app_certificate_conversion_test.go b/bp2build/android_app_certificate_conversion_test.go
index 6a53b00..035a352 100644
--- a/bp2build/android_app_certificate_conversion_test.go
+++ b/bp2build/android_app_certificate_conversion_test.go
@@ -31,11 +31,10 @@
 
 func TestAndroidAppCertificateSimple(t *testing.T) {
 	runAndroidAppCertificateTestCase(t, bp2buildTestCase{
-		description:                        "Android app certificate - simple example",
-		moduleTypeUnderTest:                "android_app_certificate",
-		moduleTypeUnderTestFactory:         java.AndroidAppCertificateFactory,
-		moduleTypeUnderTestBp2BuildMutator: java.AndroidAppCertificateBp2Build,
-		filesystem:                         map[string]string{},
+		description:                "Android app certificate - simple example",
+		moduleTypeUnderTest:        "android_app_certificate",
+		moduleTypeUnderTestFactory: java.AndroidAppCertificateFactory,
+		filesystem:                 map[string]string{},
 		blueprint: `
 android_app_certificate {
         name: "com.android.apogee.cert",