feat: CLI can delete multiple sensors at once

[Flix6x]

This PR let's you delete multiple sensors with a single call to flexmeasures delete sensor by passing the --id option multiple times. I also tried to streamline the help messages a bit for CLI usages of the SensorIDField.

[Ahmad-Wahid]

Just a thought, what if we pass a list of multiple sensor IDs and delete them. Like flexmeasures delete sensor --id [1,2] so far it's fine by passing the id multiple times.

[Flix6x]

what if we pass a list of multiple sensor IDs and delete them. Like flexmeasures delete sensor --id [1,2]

I like it, but I see the question in the context of a larger issue with how we support different ways of passing lists in various places in the CLI. In general, I like the idea of supporting different ways of passing lists:

• Using an argument multiple times (like in this PR and various other command options of the flexmeasures add CLI group, which is based on https://click.palletsprojects.com/en/8.1.x/options/#multiple-options).
• Using a comma separated list, like for instance --start-offset -3D,DB,1W in flexmeasures add report.
• Using a JSON-like string like you suggest, similar to the --attributes field in flexmeasures add sensor.

It would be nice to better streamline the use of lists in CLI options. -> I opened #736.