[TF2] Allow weapons with penetrating bullets to penetrate Medigun shield

[HyperionCoding]

Description

This change makes it so that weapons with penetrating bullets can go through the Medigun shield depending on the penetration and shield levels. This gives much more control for custom MvM mission creators over the usage of shield and penetrating heavy robots and the corresponding upgrades on the defenders.

There are two different kinds of penetration:

• projectile penetration heavy will count shield just like players but take into account the shield level (generate rage on heal) and subtract that from the penetration limit.
• projectile penetration and sniper penetrate players when charged will penetrate the shield up to level 3 without any side effects but get blocked by shield level 4 and higher. The limit is chosen because max upgraded projectile penetration heavy will also be stopped by level 4.

Currently no official mission uses shield Medics nor Heavies with penetration upgrade so this will have no effect on them.