Rewrite how to generate apexkeys.txt

Instead of listing all apexes in the source tree, now each apex emits
its own fragment for apexkeys.txt, which is pointed by
LOCAL_APEX_KEYS_FILE. Makefile collects apexkeys.txt from installed apex
files. This is to avoid listing unrelated apexes (not installed,
testdata, unexported namespaces, etc.)

Bug: 304914238
Test: m apexkeys.txt
Test: m blueprint-tests
Change-Id: Iefbe6e486cb418955584ad1a282455307e90be95
diff --git a/apex/apex_test.go b/apex/apex_test.go
index e70d3af..97cc3cb 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -9078,8 +9078,8 @@
 		}
 	`)
 
-	apexKeysText := ctx.SingletonForTests("apex_keys_text")
-	content := apexKeysText.MaybeDescription("apexkeys.txt").BuildParams.Args["content"]
+	myapex := ctx.ModuleForTests("myapex", "android_common_myapex")
+	content := myapex.Output("apexkeys.txt").BuildParams.Args["content"]
 	ensureContains(t, content, `name="myapex.apex" public_key="vendor/foo/devkeys/testkey.avbpubkey" private_key="vendor/foo/devkeys/testkey.pem" container_certificate="vendor/foo/devkeys/test.x509.pem" container_private_key="vendor/foo/devkeys/test.pk8" partition="system" sign_tool="sign_myapex"`)
 }
 
@@ -9119,10 +9119,10 @@
 		}
 	`)
 
-	apexKeysText := ctx.SingletonForTests("apex_keys_text")
-	content := apexKeysText.MaybeDescription("apexkeys.txt").BuildParams.Args["content"]
+	content := ctx.ModuleForTests("myapex", "android_common_myapex").Output("apexkeys.txt").BuildParams.Args["content"]
+	ensureContains(t, content, `name="myapex.apex" public_key="vendor/foo/devkeys/testkey.avbpubkey" private_key="vendor/foo/devkeys/testkey.pem" container_certificate="vendor/foo/devkeys/test.x509.pem" container_private_key="vendor/foo/devkeys/test.pk8" partition="system" sign_tool="sign_myapex"`)
+	content = ctx.ModuleForTests("myapex_set", "android_common_myapex_set").Output("apexkeys.txt").BuildParams.Args["content"]
 	ensureContains(t, content, `name="myapex_set.apex" public_key="PRESIGNED" private_key="PRESIGNED" container_certificate="PRESIGNED" container_private_key="PRESIGNED" partition="system"`)
-	ensureContains(t, content, `name="myapex.apex" public_key="PRESIGNED" private_key="PRESIGNED" container_certificate="PRESIGNED" container_private_key="PRESIGNED" partition="system"`)
 }
 
 func TestAllowedFiles(t *testing.T) {