perf(view): Cache only latest screen-to-terrain result

[CryoTheRenegade]

Summary

In #2815 I profiled W3DView::m_locationRequests and found that only the newest entry was reused out of the 40 entry cache. The movement (moving camera in replays) test produced 33,590 newest-entry hits, while older cached entries had no hits.

This change replaces the 40 entry cache with a single entry cache that tracks bridge and seismic additions, deletions, and damage-state changes persistently so we can invalidate the entry when a change occurs.

[greptile-apps]

Greptile Summary

This PR changes screen-to-terrain caching to keep only the latest result. The main changes are:

• Replaced the W3DView request vector with one cached screen/world pair.
• Added cache invalidation for viewport, camera, terrain, seismic, and bridge changes.
• Added bridge-change counters to both Generals and Zero Hour terrain logic.
• Removed the old position-request typedefs from the common STL typedef header.

Confidence Score: 5/5

This looks safe to merge after a small cache-invalidation cleanup.

• The main cache rewrite is internally consistent.
• Bridge damage polling can invalidate the new cache even when no bridge changed.
• No security issues were found in the changed code.

TerrainLogic.cpp in both Generals and GeneralsMD.

Important Files Changed

Filename	Overview
Core/GameEngine/Include/Common/STLTypedefs.h	Removed the old position-request cache typedefs.
Core/GameEngineDevice/Include/W3DDevice/GameClient/W3DView.h	Replaced the vector cache members with scalar fields for one cached request.
Core/GameEngineDevice/Source/W3DDevice/GameClient/W3DView.cpp	Implements the single-entry cache and invalidates it around view, terrain, seismic, and bridge changes.
Generals/Code/GameEngine/Include/GameLogic/TerrainLogic.h	Adds the bridge-change counter field and accessor.
Generals/Code/GameEngine/Source/GameLogic/Map/TerrainLogic.cpp	Adds bridge-change counter updates, with one over-invalidation issue in damage-state polling.
GeneralsMD/Code/GameEngine/Include/GameLogic/TerrainLogic.h	Mirrors the bridge-change counter API for Zero Hour.
GeneralsMD/Code/GameEngine/Source/GameLogic/Map/TerrainLogic.cpp	Mirrors the bridge-change counter implementation, including the same damage-polling over-invalidation issue.

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

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### Issue 1 of 2
Generals/Code/GameEngine/Source/GameLogic/Map/TerrainLogic.cpp:1866
**Bridge Counter Always Changes**

When `updateBridgeDamageStates()` runs, this increment advances the cache generation even if the bridge scan found no real damage-state change. `W3DView::screenToTerrain()` now treats any generation change as an invalidation, so maps with bridges can throw away the new one-entry cache every frame and lose the intended reuse.

### Issue 2 of 2
GeneralsMD/Code/GameEngine/Source/GameLogic/Map/TerrainLogic.cpp:1866
**Bridge Counter Always Changes**

This mirrored Zero Hour path also advances `m_bridgeChangeCounter` every time bridge damage states are polled, even when no bridge state changed. Since `screenToTerrain()` invalidates its cached result on any counter difference, bridge maps can miss the new cache every frame instead of reusing the latest result.

_{Reviews (1): Last reviewed commit: "bugfix(w3d): Invalidate terrain cache on..." | Re-trigger Greptile}