Burrower burrow changes and fixes

[Unknownity]

About the pull request

The PR contains mostly fixes for the Burrower that have been around, that being that other xenos could slash them while they were burrowed, that they could resist (and get rid of fire) while burrowed, that they still took shrapnel and direct flame damage while burrowed, that SG autofire and sentries were shooting at a burrowed burrower, wasting ammo in the process.

Two other notable changes are that the unburrow stun now also works on other non-friendly xenomorphs (and it works on all of them, skill issue if you manage to get stunned from that as a T3/Queen) and that burrowing and unburrowing now has sounds (a change many people were positive about when it was initially included in the Impaler PR) which may find tracking and noticing the presence of burrowers easier.

burrowing sound: https://voca.ro/1dQ0pvBMidsr
unburrowing sound: https://vocaroo.com/1zzEz3NQ2Kx5

Explain why it's good for the game

Bugfixes and a counter to one of the most annoying abilities (that people consider) in the game.

Testing Photographs and Procedure

Screenshots & Videos

Put screenshots and videos here with an empty line between the screenshots and the <details> tags.

Changelog

🆑 Unknownity
fix: Fixed burrowed mobs being able to be targeted by sentries, mines and SG autofire.
fix: Fixed burrowed mobs being able to grab mobs on the surface.
fix: Fixed burrowed mobs being able to resist while burrowed.
fix: Fixed burrowers taking damage from direct flame and shrapnel from explosions.
fix: Fixed burrowers being able to get slashed from enemy Xenos on the surface.
fix: Fixed burrowers unburrow stun to now properly target and stun enemy Xenos.
soundadd: Added sounds for the Burrower when they are burrowing and unburrowing.
/:cl:

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You currently have a negative Fix/Feature pull request delta of -7. Maintainers may close this PR at will. Fixing issues or improving the codebase will improve this score.

[github-actions]

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