General enhancements for OAuth and initial support for OpenID Connect

This was spawn from a part of QTBUG-113218

• * [Needs new API] New convenience
  • QTBUG-124330 API for accessing the granted scope while keeping the requested scope
  • QTBUG-124332 Token expiration and automatic refresh convenience
  • QTBUG-65309 Token request modification possibility
• [Needs new API] Improve redirect uri handling support
  • QTBUG-127839 Support QtWebEngine usage as the user-agent
  • QTBUG-64615 https support to QOAuthHttpServerReplyHandler
  • QTBUG-127843 Documented means to supply redirect URIs that are acquired some other ways
• [Needs new API] OpenID Connect token acquisition support
  • QTBUG-124336 Nonce support
  • QTBUG-124334 id_token property and documentation

Likely:

• QTBUG-130611 Device Authorization Grant support (new QOAuth2DeviceAuthorizationFlow class)