TOP-995: single source delay tracking integration test

This MR adds the ITC.L.AA0.5.CORR.2 integration test that is built to track a target over time using delays from the LOW CBF delay emulator. The test is supposed to observe for 15 minutes and plot the cross-correlation phase values from the captured visibilities.

Other notable changes:

• The previous method of unpacking visibility data was using way too much memory to be able to run sufficiently: unpacking a 3GB file required more than 20GB of memory, which doesn't scale at all. It has therefore been refactored to optimize memory usage.
• The unpacked visibility data is now represented using an xarray.Dataset, which is able to store the full visibility data as one big xarray.DataArray per time offset, including metadata to make the data more self-describing. This required a small change on the plotting logic to make it backward-compatible.

Open issues to address before merging:

• Agree with @r.vanrooyen on which input channels to use for this test (for now)
• Agree with @r.vanrooyen on the required CNIC-VD noise seeds