Use the same hash factory for a closed plain local

Replace parameterless MD5 CSP or SHA Managed/CSP construction in a closed plain local with the same algorithm factory. Support inferred, provider and matching algorithm types. Retain every ComputeHash and explicit BCL Clear/Dispose call at its original location. Cleanup must be a terminal sequence; skip later hashing, nested cleanup or re-entry. Skip using resources, generic bases, configuration, escapes, captures, initialization, async/iterators and snapshots. Opt-in modern-.NET compatibility; no cleanup or algorithm policy change.