feature: support API Keys

[rustatian]

Reason for This PR

• API Key public preview support. docs.

Description of Changes

• Support dynamically changing API keys.
• API key can be set by the PHP worker and updated by using UpdateAPIKey RR<->PHP RPC API.

Token can be initially set via the internal WokerInfo IPC call (flags field, ApiKey key inside the associated array) and updated via UpdateAPIKey RPC call where the first argument is a string, the second - bool (true - token changed, false - new token was empty).

License Acceptance

By submitting this pull request, I confirm that my contribution is made under
the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.]
[Reviewer TODO: Verify that these criteria are met. Request changes if not]

• All commits in this PR are signed (git commit -s).
• The reason for this PR is clearly provided (issue no. or explanation).
• The description of changes is clear and encompassing.
• Any required documentation changes (code and docs) are included in this PR.
• Any user-facing changes are mentioned in CHANGELOG.md.
• All added/changed functionality is tested.