blockifier: enable CASM migration

[dorimedini-starkware]

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[cursor]

PR Summary

Medium Risk
Flips enable_casm_hash_migration to true, which can change how class hashes are interpreted/migrated during execution and may affect network compatibility for 0.14.2.

Overview
Turns on CASM hash migration for blockifier_versioned_constants_0_14_2.json by changing enable_casm_hash_migration from false to true.

Updates the 0.14.1_0.14.2 diff-regression fixture to reflect the constant change (removing the prior expectation that the flag differs between versions).

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• Started at 2026-05-12T10:03:44Z