Share version settings with product config makefile.

Generate version settings from build/make/core/version_defaults.mk.
The generated settings are then loaded into the launcher code and passed
to the environment setup code.

Bug: 198995713
Test: internal
Change-Id: I66131d2c5b232784a9ff0bba9fbd5db62302aaba

mk2rbc/Android.bp

@@ -38,6 +38,7 @@ bootstrap_go_package {
         "soong_variables.go",
         "types.go",
         "variable.go",
+        "version_defaults.go",
     ],
     deps: ["androidmk-parser"],
 }