crypto: runtime-deprecate calling Hmac.digest() more than once (DEP0206)

[Anshikakalpana]

Refs: #62838
Refs: #63121

Situation

Calling digest() on an already-finalized Hmac instance currently returns an empty buffer silently instead of throwing an error. This is inconsistent with Hash behavior which throws ERR_CRYPTO_HASH_FINALIZED and is a potential security footgun.

Change

Add a runtime deprecation warning (DEP0206) when digest() is called more than once on an Hmac instance. The existing behavior (returning an empty buffer) is preserved during the deprecation cycle to avoid breaking changes. docs-only deprecation was introduced in #63121.

[nodejs-github-bot]

Review requested:

• @nodejs/crypto
• @nodejs/userland-migrations

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.04%. Comparing base (3c2d2e3) to head (b7bc8a8).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63162      +/-   ##
==========================================
- Coverage   90.04%   90.04%   -0.01%     
==========================================
  Files         713      713              
  Lines      224484   224505      +21     
  Branches    42430    42426       -4     
==========================================
+ Hits       202134   202146      +12     
- Misses      14156    14161       +5     
- Partials     8194     8198       +4     

Files with missing lines	Coverage Δ
lib/internal/crypto/hash.js	99.03% <100.00%> (+0.02%)	⬆️

... and 26 files with indirect coverage changes

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