Add some metadata to UVFlag

[bhazelton]

UVFlag is missing some important metadata. The spw information needs to be added to support flexible spectral windows

• spw_array
• flex_spw_id_array
• telescope_name
• channel_width
• antenna_numbers
• antenna_names
• antenna_postitions
• telescope_location
• ?? source-related parameters (phase_center_catalog, phase_center_id_array)

[bhazelton]

@kartographer any thoughts about whether we'd want to propagate phase center info to UVFlag? On the one hand, it doesn't seem too critical, but on the other it would facilitate conditioning flagging operations on phasing info.

In some ways, it seems similar to propagating the spectral window information to UVFlag.

[bhazelton]

Another question (for anyone with an opinion): If we add antenna_names and antenna_numbers, should we also add antenna_positions? Or is that not that helpful for UVFlag?