Fix placement validation and eliminate orphan bridge plans

[derekShaheen]

Problem found where bridges and sometimes extractors would be placed on invalid tiles.

PR centralizes all placement checks into a single validation layer in Util.java and add a dry-run phase so plans are only submitted to the build queue after the full set is validated.

Changes:

• Util.java — Added canPlaceBlock, canPlacePlan, canPlaceWithoutPlanCollision, footprintOverlapsPlanned, isWithinWorld, and commitPlans. All callers now funnel through these instead of ad-hoc checks.
• OptimizationDrill.java — Pre-filter candidates with full footprint validation. Dry-run all drill + water extractor + power node plans before committing. Fixed incorrect settings key mapping (mechanicalDrill was reading "laser-drill-max-tiles").
• BridgeDrill.java — Bridges are only placed if they connect to another planned bridge or an existing bridge on the map. A pruning loop removes plans whose targets were rejected, iterating until stable. Existing map bridges are recognized as valid connection partners.
• WallDrill.java — All bore, duct, beam node, and connection plans go into a shared dry-run list validated via canPlaceWithoutPlanCollision before a single commitPlans call. Fixed potential infinite loop in connecting-tile traversal.

Debug support: Util.DEBUG flag logs rejection reasons (out of bounds, overlap, Build.validPlace failure) to the Mindustry console.

Testing:

• Find a resource near uneven walls (looking for stairstepped sort of walls) and use autodrill. Find an instance where invalid bridges occur. Save game
• Update to this version, undo that building plan, place again. Bridges/extractors should place as expected.