[TF2] Gamemode prefix check fails when loading map from Workshop

[Lizard-Of-Oz]

Description

tl;dr - some map prefix checks don't account for the workshop/ prefix, which leads to problems. This PR fixes that.

When TF2 maps are loaded directly from the workshop via map workshop/<entryid>, the mapname has a different format:

koth_trainsawlaser_v3 //normal
workshop/koth_trainsawlaser_v3.ugc3566434696 //workshop

While most map prefix checks do account for this, there's a few exceptions that don't, which leads to the following observable bugs:

• Special Delivery maps don't get recognized as Special Delivery, and the game treats them as normal CTF.
• CTFPlayer::PrecacheMvM(); never gets triggered, therefore some MvM assets never get loaded/cached. Namely, footstep sounds.
• IsCustomGameMode() check for VSH and ZI fails, meaning server_custom.cfg never gets loaded and the autoteam command still works (it's meant to be disabled in those gamemodes).

Because maps are usually playtested before being uploaded to the workshop, very often these bugs don't get caught by the mappers.