Removed unused UncaughtErrorHandler.

[matux]

Description of the change

After the recent changes, we've dropped UncaughtErrorHandler, this removes it.

Type of change

• [ ] Bug fix (non-breaking change that fixes an issue)
• [ ] New feature (non-breaking change that adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] Maintenance
• [ ] New release

Related issues

Shortcut stories and GitHub issues (delete irrelevant)

• https://github.com/rollbar/rollbar-flutter/issues/56

Checklists

Development

• [x] Lint rules pass locally
• [x] The code changed/added as part of this pull request has been covered with tests
• [x] All tests related to the changed code pass in development

Code review

• [x] This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• [x] "Ready for review" label attached to the PR and reviewers assigned
• [x] Issue from task tracker has a link to this pull request
• [ ] Changes have been reviewed by at least one other engineer

[matux]

LGTM. I assume the functionality of UncaughtErrorHandler was moved to another place/class?

It wasn't doing anything.

The error listening properties of the Isolate were being used incorrectly, so only errors happening within the isolate were being caught.

The other thing the UncaughtErrorHandler was doing was initializing RollbarInfrastructure, I don't know why it was there, and it was the reason why the lib wasn't sending payloads to Rollbar.

Now everything is initialized at a single point when Rollbar starts.

[matux]

LGTM. I assume the functionality of UncaughtErrorHandler was moved to another place/class?

All the details are in the issue I created: https://github.com/rollbar/rollbar-flutter/issues/45.