add the ability to enable/disable an alert node config

[russorat]

Right now, there is no way to "unset" an alert node config in the Kapacitor UI. We should add that ability.

• determine if we can toggle enable/disable for kapa configs
• add the option to enable / disable to the ui.
• ensure we can use this to remove the deprecated notice in the UI

[russorat]

required for #2786 and #2904

[alexpaxton]

Use a ConfirmButton here to prevent accidental resets. Using the language "Reset" because all this should do is set all the values back to an unconfigured state, rather than deleting anything. This action should remove the green checkmark in the alert tab as well, which will indicate to the user that the action was effective

[alexpaxton]

Also, the use case of disabling doesn't make a ton of sense to me. Not sure why someone would want to turn off a config but preserve the values (which is what "disable" means to me) and then re-enable later

[alexpaxton]

Final Design

Notes:

• The green checkmark icon represents enabled state, the absence of a checkmark means the configuration is disabled
• Saving a configuration enables it (unchecks the checkbox)
• Checking the checkbox disables and saves the values
• Clicking delete removes the config and is only available when you have multiple configs for the same endpoint (Slack)