Html element onerror override

[cosmic-pixel-painter]

This PR fixes this Typescript issue.

Originally, I created this PR, but closed it as the that approach wasn't ideal.

I started with Omit<GlobalEventHandlers, 'onerror'> as an approach. However, I quickly realized it isn't the correct path and creates a whole slew of new problems due to how event handlers are mapped to different elements during the emit phase. (if you're curious to see what exactly I ran into, I can push up a separate PR).

What this change does:

• Introduces a new type DocumentOrGlobalOnErrorHandler which extends the OnErrorEventHandlerNonNull type with HTMLElement specific handlers. This type then overrides GlobalEventHandlers onerror property. This allow us to be backwards compatible and fix the bug.

• This did require a change to both types.ts and emitter.ts so that exposed was accounted for when creating a new typedef. I needed the new DocumentOrGlobalOnErrorHandler to only be exposed on the dom library.

• the onerror of GlobalEventHandlers cannot be overridden by the overrideType.ts file. I tried to a few times, in both mixin-ins and interfaces. It turns out it has to be overidden in the patches/events.kdl file.

Let me know if I missed anything or another approach would be better. I think this threads the needle nicely as it works only on dom elements and still provides both the global and HTMLElement specific onerror handling types.

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @saschanaz - if they write a comment saying "LGTM" then it will be merged.