tls: remove tls_legacy, createSecurePair

[jhamhader]

Pull Request check-list

Please make sure to review and check all of these items:

• Does make -j8 test (UNIX) or vcbuild test nosign (Windows) pass with
  this change (including linting)?
• Is the commit message formatted according to CONTRIBUTING.md?
• If this change fixes a bug (or a performance problem), is a regression
  test (or a benchmark) included?
• Is a documentation update included (if this change modifies
  existing APIs, or introduces new ones)?

NOTE: these things are not required to open a PR and can be done
afterwards / while the PR is open.

Affected core subsystem(s)

Please provide affected core subsystem(s) (like buffer, cluster, crypto, etc)

Description of change

Please provide a description of the change here.

This is a semver-major change.
Remove SecurePair, createSecure pair from API.
Remove internal Connection class and SecurePair tests.

[mscdex]

I don't think this can be removed without some sort of deprecation cycle.

[jhamhader]

1. I pushed that after an IRC talk with @indutny
2. Resolving conflicts in a few seconds

[jasnell]

A deprecation cycle would definitely be required first.

[indutny]

@jasnell what exactly is missing? I believe createSecurePair had a deprecation warning in documentation for quite a long time now...

[mscdex]

@indutny I think it needs to be deprecated at the code level via internal/util.deprecate() and not just documentation. Also, tls.createSecurePair() isn't even deprecated in the documentation.

[indutny]

@mscdex perhaps there is a bug in docs, but it is deprecated: https://nodejs.org/api/tls.html#tls_class_cryptostream

[mscdex]

@indutny There is no connection between CryptoStream and createSecurePair()/SecurePair in the docs.

[indutny]

@mscdex yeah, looks like we will need to deprecate it first then. 😢

@jhamhader sorry, but this PR will have to wait a release cycle

[jhamhader]

Will submit a deprecation PR and resume effort on SNI callback issue.
Thanks

[jasnell]

Closing in favor of #11349