Add cvar to automatically mute low-tour players in MvM

[k-vog]

This adds a new cvar tf_mvm_tour_mute_threshold to automatically mute players below a certain tour count in Mann Up mode.

[JoriKos]

This adds nothing of value and would be an objective detriment to the game.

[mountainflaw]

lol. lmao even.

[mastercoms]

Request to add a tf_mvm_tour_mute_threshold_max, so that we may mute players above a certain tour count ❤️

[dilbertron2]

never cook again

[pizzaperp95]

maybe valve shouldn't have open-sourced the TF2 branch after all...

[Brain-dawg]

make voice chat 2% louder per-tour

a 2000 tour player speaking should trip the players circuit breaker from the power surge to their speakers.

[num-get]

Pay to gamble was a mistake.

[Bloxxel64]

Little do they know that there are probably some low tour players that are more civil than the High tour ones

[GrubPL]

Should we really give players an option to mute new players who might potentially be just asking for advice, if people want to just mute the obnoxious ones, just mute them manually, there's no need to mute actually nice people just because they're new, like I guess imagine someone asking what upgrades to pick, and never getting a response because nobody in that lobby got the message