Renamed RollbarCrash interface to RollbarCrashHandler

[matux]

Description of the change

When integrating the SDK as a Framework through SPM, Swift has trouble understanding the difference between the RollbarCrash module and RollbarCrash interface

This PR renames the main RollbarCrash interface from RollbarCrash to RollbarCrashHandler

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)
• Maintenance
• New release

Related issues

• Attempts to address SwiftVerifyEmittedModuleInterface error when compiling RollbarReport with Framework Target #328.

Checklists

Development

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

Code review

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