[MLIR][CF] Avoid collapsing blocks which participate in cycles (#160783)

Previously, collapseBranch did not return failure for successor blocks which were part of a cycle. mlir-opt --canonicalize would run indefinitely for any N-block cycle which is kicked off with an unconditional jump. The simplifyPassThroughBr transform would continue alternating which block was targeted in ^bb0, resulting in an infinite loop.

collapseBranch will not result in any useful transformation on blocks which participate in cycles, since the block is aliased by a different block. To avoid this, we can check for cycles in collapseBranch and abort when one is detected. Simplification of the cycle is left for other transforms.

Fixes #159743.

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