Refactor projectmetadata into separate package.

Replace regular expressions to extract fields from a text proto with
and actual parsed protobuf.

Refactor TestFS into its own package, and implement StatFS.

Test: m droid dist cts alllicensemetadata

Test: repo forall -c 'echo -n "$REPO_PATH  " && $ANDROID_BUILD_TOP/out/host/linux-x86/bin/compliance_checkmetadata . 2>&1' | fgrep -v PASS

Change-Id: Icd17a6a2b6a4e2b6ffded48e964b9c9d6e4d64d6