Refactors projectile ricochets (#25764)

* same taste, twice the speed

* pulls proc/handle_ricochet() to the atom level. adds var/flags_ricochet and related defines.

* space indentation sneaks its way in yet again

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Co-authored-by: Luc <89928798+lewcc@users.noreply.github.com>

code/game/objects/structures/window.dm

@@ -8,6 +8,8 @@
 	anchored = TRUE
 	flags = ON_BORDER
 	flags_2 = RAD_PROTECT_CONTENTS_2
+	flags_ricochet = RICOCHET_HARD
+	receive_ricochet_chance_mod = 0.5
 	can_be_unanchored = TRUE
 	max_integrity = 25
 	resistance_flags = ACID_PROOF