Request: Use non-locking read on images

[keflavich]

I frequently use CARTA to inspect files somewhere during the imaging process, e.g., to decide if more cleaning is needed.

Because CARTA loads images using locking, CASA gets blocked:

2022-05-10 12:49:39     INFO    MPICommandServer::command_request_handler_service::::::MPIServer-20     Process 47451: waiting for write-lock on file /blue/adamginsburg/adamginsburg/almaimf/workdir/G333.60_B6_spw1_12M_spw1.model/table.lock

This has on several occasions resulted in CASA sessions hanging indefinitely because I didn't realize a CARTA window was open (e.g., left open on my home machine while I'm at work). This is a user error, but it would be convenient to make the reads non-blocking. I believe this can be done with casa-formats-io, though I'm not sure it's possible to incorporate that into CARTA's backend right now.

[kswang1029]

also #169