JIT: clear loop iter info after rebuilding loops for opt repeat (#95879)

This info gets computed when finding loops but is not used by the
general optimizer (it only cares about loop structure, not iteration
details). If we leave it built it can go stale.

Fixes #95843.

src/coreclr/jit/compiler.cpp

@@ -5898,7 +5898,9 @@ void Compiler::RecomputeLoopInfo()
     fgComputeReachability();
     optSetBlockWeights();
     // Rebuild the loop tree annotations themselves
+    // But don't leave the iter info lying around.
     optFindLoops();
+    optClearLoopIterInfo();
 
     m_dfsTree = fgComputeDfs();
     optFindNewLoops();