Add linter option to disable all rules

[jake8655]

Description

Currently the linter.rules.all option accepts a boolean:

• true -> enable all rules (except nursery)
• false -> don't enable all rules (default)

It would be nice to instead have the option to enable or disable all rules as such:

• "on" -> enable all rules (except nursery)
• "off" -> disable all rules
• not set -> default (same as false in the current version)

Use case

You want to disable all rules except some that you manually whitelist by setting them to "warn" or "error".

[ematipico]

You can achieve what you want by disabling the recommended rules. Is that correct?

[jake8655]

@ematipico Yes! Thank you for pointing this out, I didn't know that.

In that case, there's no need for my proposed changes. Maybe there could be a small note about this somewhere in the docs though, as it doesn't seem to be that intuitive at first. What are your thoughts on that?

[ematipico]

We welcome any change that could help making things clear

[jake8655]

Alright, I will create a PR shortly then.

Thank you for your help!