Store SourceTV in m_vecPlayers

[Vauff]

Poggu has suggested keeping SourceTV in our players vector for consistency following 892bb8e, this would require adding SourceTV checks everywhere we access ZEPlayer, and an assert when using GetZEPlayer() on SourceTV.

It's worth considering that we'd be very likely to miss adding these checks in future development, as no CS2Fixes servers/developers are even running SourceTV to find these issues (it was broken until today). This may be less of an issue further down the road, if/when more CS2Fixes servers actually start using SourceTV, and report these issues as they appear.