[Bugfix] Fix Missile obstruction checks

[kphoenix137]

Fixes: #6693

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LineClearMissile()
Monsters ask:

"Can I shoot the player?"

1. LineClear(PosOkMissile, start, end)
2. PosOkMissile(tile) = true if the tile is not BlockMissile.

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CheckMissileCol()
Missiles ask:

"Can I move through this tile?"

1. !IsMissileBlockedByTile(tile)
2. false if:
   • out of bounds
   • tile has BlockMissile
   • there’s an object with _oMissFlag == false

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To remedy this, this PR adds a variant function called LineClearMovingMissile(), which is exclusively used when we need to check if a missile would be able to make it between 2 points without hitting an obstruction according to CheckMissileCol(). LineClearMissile() continues to be used for missiles that do not need to travel, such as Leoric summoning a minion at a position, or the player casting a Guardian at a position.

This fix has edge cases due to differing logic between LineClear() and how a missile moves along a path with MoveMissile(). This is the 2nd of the 4 needed fixes for the the problems with ranged monsters/ranged spells (like Guardian), and the 1st already has been merged back in 2023.

1. Missile Space Distortion fix
2. Same checks for missile path success and confirming missile path has no obstructions (This PR)
3. Same logic for missile path and confirming missile path has no obstructions
4. Ranged monster AI tweaks to prevent standing still with no valid line of sight for missiles

[strich]

Code changes look good to me. It is unclear yet if this fully resolves the linked bug, though it is mentioned more work needs to be done after this as well in the OP post.