Fix testSphereAgainstWorld returning nil hitElement for buildings

[TheCrazy17]

Summary

Fixes hitElement returning nil when testSphereAgainstWorld (and processLineOfSight) hits a building created with createBuilding.

Motivation

Resolves #5136. CPoolsSA::GetEntity never checked the buildings pool, so CEntity* resolution for a building always fell through to null. Even after that, testSphereAgainstWorld still returned nil because it resolves its element through GetStoredPointer, which CClientBuilding::Create never set on the native entity, unlike objects, peds and vehicles.

Test plan

Created a building with createBuilding, called testSphereAgainstWorld and processLineOfSight against it. Before the fix, both returned a hit with a nil hitElement; after the fix, hitElement correctly resolves to the building.

Checklist

• Your code should follow the coding guidelines.
• Smaller pull requests are easier to review. If your pull request is beefy, your pull request should be reviewable commit-by-commit.

[FileEX]

What about CPoolsSA::GetClientEntity method?