Escalation picker fixes and improvements

[moonysolari]

This PR addresses several issues of the escalation picker:

• Improved the error handling by allowing the frontend to show errors messages in the console and push error alerts to the user.
• Added more error types and corresponding error messages.
• Prevents the level shown on the picker to exceed the maximum level of the escalation, or to go below 1. An alert is shown when the user attempts to do either of these.
• Fixed the id of The Baskerville Barney in static/EscalationCodenames.json. It previously had the same id as the Dartmoor Garden Show.
• Alerts the user upon attempts to set the level for unregistered escalations, likely due to the user not having the Legacy Escalations plugin.

Besides these, it also:

• Fixes the error message shown when PEACOCK_DEV is set to true and the user attempts to visit localhost.

It does not add peacock-exclusive escalations.

[moonysolari]

Side note: Currently there are two files where escalation information resides: static/EscalationCodenames.json and components/contracts/escalationMappings. While I see the reason for having two files, it brings several inconveniences:

• It is more error-prone (the id of The Baskerville Barney).
• Efforts have to be made to update one when the other is changed, hence the need to "add" peacock-exclusive escalations to the picker.
• If a plugin adds new escalations, they will not show up on the picker.
• The picker will still show escalations that is only supported by a plugin even if the plugin is not installed (e.g. legacy escalations plugin)

It is high time that this setup be reconsidered, now that the escalation system is under rework.

[RDIL]

If a plugin adds new escalations, they will not show up on the picker.

If a plugin explicitly adds an escalation to the list, then it will.