Add support for Closes tags with custom Bugzilla resolution

This PR is part of a larger effort[1] to automate resolving bugs on Gentoo's Bugzilla with the correct resolutions. The command line syntax would be: * `<bug>:<resolution>` for a given bgo bug with an explicit resolution * `<bug>:` or `<bug>` for any bug without a resolution (implicitly `FIXED` for a bgo bug) Apart from `FIXED`, I chose to support: * `OBSOLETE` e.g. for when older versions of a package get dropped which implicitly fixes a bug * `PKGREMOVED` to encourage its adoption for the removal of packages If you think any resolutions are missing here, please tell me! I wasn't sure how to handle malformed URL-like input with multiple colons like `https://foo:bar:obsolete`. Currently, it gets converted into a `Closes: https://foo:bar (obsolete)` tag, similar to how `-T/--tag` does it. --- [1]: Patch for infra's githooks: https://bugs.gentoo.org/934825