Multikey peer authentication sender integration

[sstanculeanu]

Description of the reasoning behind the pull request (what feature was missing / how the problem was manifesting itself / what was the motive behind the refactoring)

• peer authentication sender is not compatible with the multikey system

Proposed Changes

• integrate keysHolder into newly added component multikeyPeerAuthenticationSender in order to support multikey
• updated keysHolder with the needed methods
• factory which will create the proper one(multikeyPeerAuthenticationSender or peerAuthenticationSender) will come in a further PR

Testing procedure

• system test hbv2