Show package details on the retry page

Previously, only the Retry button was visible to trigger the autopkgtest.
But with this, package details, like, name, suite, arch, et al, will be shown to the end-users, too.

Right now, it looks something like this:

I am not sure how the last two boxes should look like :)

I wasn't very sure about this, but here's my first hack.
Also, thanks to Akanksha's original MR, I took some HTML hints from there. So I should not have all the credits myself :)
Closes: #25 (closed)