Adding a metadata flag for signaling successful ingestion

[ktsitsi]

This PR:

• Adds a metadata KV at a group level of an ingested image signalling if the ingestion was completed successfully after all the steps.
• The metadata key valid gets a boolean value of either True or False
• During every ingestion a check is being performed to find if the desination path already exists and is a group. In this scenario we check if the group's metadata contain the key valid. If not this signals a corrupted ingested file (possibly from a previous run) and the response to that is for the group to be overwritten from scratch.
• In case the group exists but the ingestion runs in order for more layers to be added into the image incremental ingestion the flag is not enabled. We initially remove again the valid KV from the group's metadata until re-instantiate at the end of the current ingestion that is being running.

[spencerseale]

Should overwrite be an arg that defaults to False? That would give us flexibility to overwrite every image. Although uncommon, may be times when we need to force overwrite. Could then make that arg accessible from tiledb.cloud.bioimage.ingest as well.

[spencerseale]

The caveat would be of course that if an image is invalid it will still be overwritten even if overwrite=False set in the caller

[ktsitsi]

Yeap the direction of this patch is to mitigate retrial issues and corrupted leftovers, that the user fails to recognize. If users really want to overwrite/re-ingest an image on purpose they can always do it by changing the destination path and manually deleting the previous record.