port: [#6677][Teams] Add support for meeting participants added/removed events

[ceciliaavila]

The changes in [#6677][Teams] Add support for meeting participants added/removed events may need to be ported to maintain parity with microsoft/botbuilder-dotnet.

#minor

Description

This PR is based on #5809. It adds support to TeamsActivityHandler for meeting participant join/leave events.

Specific Changes

• Added support for 2 new activity types - application/vnd.microsoft.meetingParticipantJoin and application/vnd.microsoft.meetingParticipantLeave.
• Added functions to register handlers for when teams meeting participants are joined/left.
• Added unit tests.

Testing

These images show the new unit tests passing and the implementation tested with a sample.