don't refetch releases lists in platform & versions ajax partials

[syphar]

I saw this while looking at other code in the web handlers.

• We already fetch the list of all releases in match_version, so we don't need to do it again in the web handlers. Since fetch CrateDetails via MatchedRelease to save one SQL query per request #2435 we store the list on our matched release too.
• we were also fetching too much information in the sql statements that we already have
• secondly I saw places where crates.name was used in generating an inner path, while target_name is what we need here.