Move ClassLoaderContexts() method to UsesLibraryDependency interface.

This method logically belongs with other UsesLibraryDependency methods,
as it is used in the same context when computing class loader context.
Previously it was part of Dependency interface, which doesn't cover SDK
libraries. We do not currently have the necessary information for
SdkLibraryImport (so ClassLoaderContexts() returns nil for it), but we
do have it for SdkLibrary (via Library).

Bug: 132357300
Test: m nothing
Change-Id: I56437f260efc6a9af3f45b334e84e915244ccce1

java/java.go

@@ -510,6 +510,7 @@ type ApexDependency interface {
 type UsesLibraryDependency interface {
 	DexJarBuildPath() android.Path
 	DexJarInstallPath() android.Path
+	ClassLoaderContexts() dexpreopt.ClassLoaderContextMap
 }
 
 type Dependency interface {
@@ -518,7 +519,6 @@ type Dependency interface {
 	ImplementationJars() android.Paths
 	ResourceJars() android.Paths
 	AidlIncludeDirs() android.Paths
-	ClassLoaderContexts() dexpreopt.ClassLoaderContextMap
 	ExportedPlugins() (android.Paths, []string, bool)
 	SrcJarArgs() ([]string, android.Paths)
 	BaseModuleName() string