Use the same hash factory inside an existing using block

Replace parameterless MD5 CSP or SHA1/SHA256/SHA384/SHA512 Managed/CSP construction in using(var hash = new ...) with the same algorithm's Create() factory, retaining disposal and repeated ComputeHash calls. Require all references to be bound BCL ComputeHash receivers. Skip configuration, identity, escapes, other members, captures, async/iterators and conditional snapshots. Opt-in modern-.NET compatibility port; no algorithm strengthening.