Use static_lazy() for images in the trophy class definitions.
Use static_lazy() for images in the trophy class definitions.

The trophy classes were using `static()` to specify the images for the
various DPIs for each trophy. This ended up causing static lookup state
to be initialized too early, breaking extension packaging.

To fix this, we now use the new `static_lazy()` found in Djblets, which
will let us reference the static media we want, but actually perform the
lookups on demand at runtime.

Testing Done:
Tested building an extension with static media. It built successfully.

Reviewed at https://reviews.reviewboard.org/r/8419/

davidt/reviewboard,davidt/reviewboard,davidt/reviewboard,brennie/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,chipx86/reviewboard,brennie/reviewboard,sgallagher/reviewboard,brennie/reviewboard,chipx86/reviewboard,brennie/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,davidt/reviewboard,sgallagher/reviewboard,sgallagher/reviewboard,reviewboard/reviewboard