verify-release-ready: improve execution time for tags checks
Going through `git tag --contains <>` is very slow in case where
there is lots of tags, and can be replaced by `git describe --exact-match`
to have faster results
Launchpad knows where we should dput the sources for a given crank. Add
an option to ask LP what the correct destination is based on the state
of the tracking-bug file.
Add a new magic destination named auto that will query SWM for the
proper stream to upload to. The built.route-entry property only recently
became mandatory so treat both missing and build.route-entry=1 as the
default stream 1.
Add a helper that can read one or more SWM properties from a tracking
bug. One or more keys must be specified in the query. An empty line is
returned for any requested key that is not found on SWM.
