sourcedr: Add manifest split analyzer

This commit adds a manifest split analysis tool.  This tool classifies
the Android.bp modules into 3 categories (i.e. system-only modules,
vendor-only modules, and both-side module) and list the git repositories
that define modules in two or more categories.

Test: analyze_manifest_split.py \
  -m ${ANDROID_BUILD_TOP}/.repo/manifest.xml \
  -b ${ANDROID_BUILD_TOP}/Android.bp

Change-Id: I74c4acc3cac8fc2795cbc03806e71685e1910818