[LinearSystem] MatrixProjectionMethod : add checks while adding to GlobalMatrix (in debug)

[fredroy]

advised by Claude while trying to fix

• [LinearSystem] MatrixProjectionMethod: Fix out-of-bounds matrix writes #6256

I set only the checks only in debug to avoid loss of perf but maybe it could enabled in any case 🤔

[with-all-tests]

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[alxbilger]

Tested with a problematic scene. I got the following error:

[ERROR]   [MatrixProjectionMethod] A projected matrix block of size 120x960 placed at (0, 1080) does not fit into the global matrix of size 1200x1200. The block is ignored.