Split SYSTEMSERVERCLASSPATH entries from platform_bootclasspath.

Boot jars are different to system server jars at build level, due to
added complexity of dexpreopt. As a logical separation add a new
classpath fragment type and split existing classpaths.proto generation
into relevant pieces.

Bug: 180105615
Test: m && launch_cvd; atest CtsClasspathsTestCases
Change-Id: I88bec09fc920166ffd0092faef980754ddeb6593
diff --git a/java/platform_bootclasspath.go b/java/platform_bootclasspath.go
index 1acb9f4..1f24942 100644
--- a/java/platform_bootclasspath.go
+++ b/java/platform_bootclasspath.go
@@ -72,8 +72,8 @@
 func platformBootclasspathFactory() android.SingletonModule {
 	m := &platformBootclasspathModule{}
 	m.AddProperties(&m.properties)
-	// TODO(satayev): split systemserver and apex jars into separate configs.
-	initClasspathFragment(m)
+	// TODO(satayev): split apex jars into separate configs.
+	initClasspathFragment(m, BOOTCLASSPATH)
 	android.InitAndroidArchModule(m, android.DeviceSupported, android.MultilibCommon)
 	return m
 }