Fix heal target marker disappearing while using Ubercharge

[Squid-Eevee]

Adds extra checks to tf_weapon_medigun.cpp so the weapon checks if the local player has the heal target marker setting (hud_medichealtargetmarker) enabled while using an Ubercharge and if so, use a separate particle system. This fixes this issue where the target marker disappears when deploying an Ubercharge.
The relevant particle files with the new particle systems can be downloaded here. I have also taken the opportunity to add the missing trail_stage3 particles to the DirectX 8.0 version of the invun beams, fixing this issue.