Link to the QA policy guide when QA notices are triggered

[sin-ack]

QA Notices are nice but it's really hard to find the appropriate documentation for them if you don't know where to look. The QA policy guide can't be found through search engines even if you search for the exact words from the notice. For instance, searching for "QA Notice: Pre-stripped files found" only brings up some unrelated results instead of https://projects.gentoo.org/qa/policy-guide/installed-files.html#pg0301.

It would be much nicer if this was directly hyperlinked to save a lot of time for new packagers (like me!).

It was suggested on IRC that special ANSI escapes for hyperlinks be used to avoid clutter. This can certainly be done but:

1. Not all terminals support this, there needs to be a fallback to printing the URL based on termcap
2. Some terminals like kitty don't style links at all until they are hovered, so we would need to style it like an URL in the terminal to draw attention (perhaps underscoring? not sure if ANSI escapes can do this)

[sin-ack]

cc @thesamesam