feat(network-weapon): allow firing multiple projectiles in a single batch

[Nyx255]

Overview

This PR introduces the ability to fire multiple projectiles in a single RPC roundtrip for NetworkWeapon. It aims to optimize network traffic for weapons that shoot multiple projectiles simultaneously (e.g., shotguns or burst patterns).

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Key Changes

• Added batch firing capabilities (fire_multiple, _after_fire_multiple, _configure_multi_projectile) to support multi-projectile execution in a single RPC.
• Extended _NetworkWeaponProxy with callables (c_after_fire_multiple, c_configure_multi_projectile) to ensure full functionality for proxy-based setups.
• Kept existing single-shot methods (fire(), _after_fire(), etc.) fully intact to guarantee 100% backward compatibility.

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Architectural Considerations & Discussion Points

1. Backward Compatibility vs. Code Duplication

Currently, single-shot and multi-shot methods exist side-by-side, which introduces some code duplication.

• Alternative considered: Merging into a single unified method signature like fire(projectile_count: int = 1) -> Array.
• Reason for current approach:
  1. Returning a 1-element Array for single shots would introduce breaking changes to existing setups.
  2. GDScript typing constraints (e.g., overriding Array[Node] vs Array[Node2D]) limit clean sub-typing without extra overhead or type cast issues.
• Question for maintainers: Would you prefer keeping the dedicated batch methods to preserve full backward compatibility, or should we refactor the existing single-shot methods into a single unified array-returning API?

2. _NetworkWeaponProxy Implementation

• Added the multi-shot callables to _NetworkWeaponProxy. I would appreciate a quick review to ensure this aligns with the intended proxy pattern design.

3. Hitscan Weapons Integration

• I am currently unsure how or if this batching concept should apply to hitscan implementations, as they don't spawn distinct projectile nodes in the same way.
• Any guidance or preference on how hitscan multi-shot should be structured within Netfox would be very helpful!

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TODO / Next Steps

• Local testing
• verification
• Gather feedback on API / duplicate code vs. breaking changes
• Clarify hitscan integration scope