Allow user to choose if an error has been handled by an ErrorBoundary

[HHK1]

Problem Statement

#8914 was setting errors caught by ErrorBoundaries as unhandled.
Then, #10985 was opened, asking to use the fallback property in order to decide if the error should be considered handled or not, and implemented in #10989.

I'm in a situation where I do not want to mark my errors as handled, despite using an ErrorBoundary. The reason is that it's a global error boundary, and at that point I consider that it's equivalent to a crash. I want to include that in my Sentry issues when filtering with unhandled, and I want to have it count towards the crashed sessions.

Solution Brainstorm

Modify the existing ErrorBoundary to pass an explicit handled property, defaulting to undefined.

For retro-compatibility the presence of the fallback property should be used if handled is not set, otherwise the setting should be used directly to mark the error as handled or not.

[Lms24]

Hey @HHK1 thanks for writing in! This sounds reasonable to me. Are you interested in opening a PR to contribute this? If not, no worries, I can take a look. Just asking :)

[HHK1]

Interested in opening a PR. From the looks of the previous implementation, it doesn't look like much.
I'll get to it right now