Log bp2build_metrics .pb

Also share `Save(pb proto.Message, filepath string)`

Bug: 201539536
Test: bp2build_metrics.pb has expected content & path
Test: m nothing
Test: {bp2build,mixed_{libc,droid}}.sh
Test: CI
Change-Id: I7d8ad87fca6a4b0355010090a527f5ae67b27c88
diff --git a/bp2build/Android.bp b/bp2build/Android.bp
index 9b66354..337fe86 100644
--- a/bp2build/Android.bp
+++ b/bp2build/Android.bp
@@ -19,6 +19,7 @@
     deps: [
         "soong-android",
         "soong-android-soongconfig",
+        "soong-shared",
         "soong-apex",
         "soong-bazel",
         "soong-cc",
@@ -27,6 +28,7 @@
         "soong-genrule",
         "soong-python",
         "soong-sh",
+        "soong-ui-metrics",
     ],
     testSrcs: [
         "android_app_certificate_conversion_test.go",