Fix updating mod version if file hash is the same

[aecsocket]

Cause:

• Dynamic Lights has the following versions:
  • Ag9747sk for Forge with file hash f02d2bcb995ee5531555995d6625571bc7f3518fa3f5e45bba230d08cd89a608
  • Yyh6uR59 for Forge + NF with file hash f02d2bcb995ee5531555995d6625571bc7f3518fa3f5e45bba230d08cd89a608
  • Two versions, but the file hashes are the same
• User downloads Dynamic Lights version Ag9747sk, downloading the f02d… file hash
• When we scan the instance mods directory to see what mods are installed, we find f02d…
• We ask the backend to see what version this file hash corresponds to - it tells us Yyuh6uR59
• We ask the backend to see what updates are available - Ag9747sk is available
• Therefore, we always update to the "new version", but it's actually the same version, and app gets confused

Solution:

• When app requests version info for a file hash, return all versions associated with it, not just the last one inserted into the map
• When setting the update_version_id, iterate through all versions, not just the first one we find()

[fetchfern]

Would maybe emphasize on the fact duplicate files are a rare edge case but otherwise LGTM

[aecsocket]

Would maybe emphasize on the fact duplicate files are a rare edge case but otherwise LGTM

IMO rarity of this doesn't really matter, if it's a possible edge case then it should be treated as important as any other path.

But since we are changing the assumption that 1 hash = 1 version, I'm not confident that this is the only place where we have this assumption. There might be more places where we assume this, and will need to change later.

Should fix #4250 though.