DISPATCH-1751: Rework how AMQP session incoming-window is derived

Proton allows specification of a session 'capacity'. Initially the
incoming-window will be (capacity / max-frame-size), defining at most
how many max-size transfers will definitely be accepted on the session.

Dispatch listener config defines a maxFrameSize and a maxSessionFrames
the product of which is equal to the capacity to be configured in Proton.

Dispatch vhostUserGroup policy defines a maxFrameSize and a
maxSessionWindow. The maxSessionWindow is passed directly to Proton
as the capacity.

This closes #847
2 files changed