Add RuleBuilder helper functions for built and prebuilt tools

Replace the common pattern of:
cmd.Tool(ctx.Config().HostToolPath(ctx, "tool"))
with:
cmd.BuiltTool("tool")

And similarly for PrebuiltBuildTool.

Test: m checkbuild
Change-Id: I7d63188505362c7df6a3b3e7330b4a2cca5a2409

java/sdk.go

@@ -296,7 +296,7 @@ func createSdkFrameworkAidl(ctx android.SingletonContext) {
 			rule.Command().
 				Text("rm -f").Output(aidl)
 			rule.Command().
-				Tool(ctx.Config().HostToolPath(ctx, "sdkparcelables")).
+				BuiltTool(ctx, "sdkparcelables").
 				Input(jar).
 				Output(aidl)