crypto: add optional callback to crypto.diffieHellman

[panva]

This adds optional callback for the stateless crypto.diffieHellman method to allow for the crypto execution to happen in libuv's threadpool.

In the asynchronous case, the OpenSSL code/library/reason error decoration is missing (because it relies on retrieving details from OpenSSL's error queue, which does not work across threads), this is something we will have to refactor in a semver-major with a broader callback methods error handling reimagining (as I've discussed privately with @tniessen), this is likely a larger endeavor now that ncrypto is in the mix.

cc @jasnell

[nodejs-github-bot]

Review requested:

• @nodejs/crypto

[jasnell]

Initial read through looks good. Will do a full review pass and sign off once it's not draft.

[panva]

Before anyone jumps the gun, despite CI possibly passing (soon-ish) - I'd like this to wait for @tniessen's review.

[codecov]

Codecov Report

Attention: Patch coverage is 85.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 90.24%. Comparing base (6b0af17) to head (47f7784).
Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
src/crypto/crypto_dh.cc	64.28%	0 Missing and 5 partials ⚠️
lib/internal/crypto/diffiehellman.js	96.15%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #57274      +/-   ##
==========================================
- Coverage   90.24%   90.24%   -0.01%     
==========================================
  Files         630      630              
  Lines      184908   184915       +7     
  Branches    36181    36197      +16     
==========================================
+ Hits       166874   166876       +2     
+ Misses      11061    11042      -19     
- Partials     6973     6997      +24     

Files with missing lines	Coverage Δ
lib/internal/crypto/diffiehellman.js	98.74% <96.15%> (+1.14%)	⬆️
src/crypto/crypto_dh.cc	64.79% <64.28%> (+3.21%)	⬆️

... and 24 files with indirect coverage changes

[panva]

Let me see if I can do more for coverage

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/65558/