Separate cc_library_headers to its own file and add tests

Preparation for adding cc_library_headers to sdk.

Bug: 148933848
Test: m nothing
Change-Id: Icbc86b21f44dc79393b82be339cf3b133cbf9d8c
diff --git a/cc/testing.go b/cc/testing.go
index 368580f..a22763a 100644
--- a/cc/testing.go
+++ b/cc/testing.go
@@ -25,6 +25,7 @@
 	RegisterCCBuildComponents(ctx)
 	RegisterBinaryBuildComponents(ctx)
 	RegisterLibraryBuildComponents(ctx)
+	RegisterLibraryHeadersBuildComponents(ctx)
 
 	ctx.RegisterModuleType("toolchain_library", ToolchainLibraryFactory)
 	ctx.RegisterModuleType("llndk_library", LlndkLibraryFactory)