Use Toasts for Success and Error Alerts

[evantahler]

This PR swaps our rather aggressive ErrorAlert and SuccessAlerts for Toasts! These toasts are 'pinned' to the UI (position:fixed) so you see them no matter where you are in the UI. Like before, they fade away after 4 seconds.

This PR collapsed the APIs of SucessHandler and ErrorHandler to be the same, accepting the "message" to show to the user. This PR does not modify any of the content of these messages, except for removing a starting Error: on error messages

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For Reference, here's what things used to look like:

Checklists

Development

• Application changes have been tested appropriately

Impact

• Code follows company security practices and guidelines
• Security impact of change has been considered
• Performance impact of change has been considered
• Possible migration needs considered (model migrations, config migrations, etc.)

Please explain any security, performance, migration, or other impacts if relevant:

Code review

• Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached where applicable.
• Relevant tags have been added to the PR (bug, enhancement, internal, etc.)

[edmundito]

Great to see this, looking much better than before.

[evantahler]

Updated in 2610ca0 with some better types and hook logic

[krishnaglick]

Seems fine, I'd be inclined to stringify the errors on the way in but we might want to keep them intact in case we need them later.

[krishnaglick]

Nitpick. This could be:
const formatMessage = (message: string | Error) => String(message).replace("Error: ", "");

[evantahler]

The startsWith check seemed important, as I didn't want to mess with There was an Error: you broke it (unlikely with that capital E in there, but you never know... it's an error).