Refactor upload-only to process bazel metrics outside of upload.go

Bug: 279987768
Test: m nothing
Test: b build libcore:all (with prints to verify similiar data)
Change-Id: I01d960a7215be30728c9e90f52c2455fd21cf1b8
diff --git a/ui/build/Android.bp b/ui/build/Android.bp
index b79754c..959ae4c 100644
--- a/ui/build/Android.bp
+++ b/ui/build/Android.bp
@@ -46,6 +46,7 @@
         "soong-ui-tracer",
     ],
     srcs: [
+        "bazel_metrics.go",
         "build.go",
         "cleanbuild.go",
         "config.go",