Consider handling googlesource.com URLs in url2purl

[JonoYang]

We should consider creating Package URLs for googlesource URLs. For example:

https://chromium.googlesource.com/v8/v8.git/%2Barchive/refs/heads/6.4.388.tar.gz

would be

pkg:googlesource/chromium/v8/[email protected]

Where googlesource is the type, chromium is the namespace, v8/v8 the name, and 6.4.388 the version.

Likewise:

https://android.googlesource.com/platform/system/bt.git/+archive/67f5f372.tar.gz

would be

pkg:googlesource/android/platform/system/bt@67f5f372