Resolve "support new ICAT communication in Flint"

Closes #2952 (closed)

Use the ICAT client in Flint instead of the tango proxy because the tango servers are deprecated (but still supported).

As far as understand @valentin.valls you don't want Flint to access the current session's SCAN_SAVING parameters in Redis. That's why the proposal and beamline name are passed to Flint at startup. Because of that Flint is restarted automatically when switching proposal.