[firebase_crashlytics] Do not break debug log formatting.

[ened]

Description

firebase_crashlytics should keep debug traces readable in debug mode.

Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See [Contributor Guide]).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (flutter analyze) does not report any problems on my PR.
• I read and followed the [Flutter Style Guide].
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I updated pubspec.yaml with an appropriate new version according to the [pub versioning philosophy].
• [] I updated CHANGELOG.md to add a description of the change.
• I signed the [CLA].
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
• No, this is not a breaking change.

[ened]

This PR is incomplete I think. The debug logs are still severely hurt when the crashlytics plugin is activated. Need to re-check.

[kroikie]

@ened Could you give more context around what you expect and what you are seeing?

[ened]

When the plugin is installed, but not activated (in debugging), I expect the exception traces to be in 100% same format as before installing the plugin. Currently, the traces are garbled / unreadable. I tried fixing that but had to stop due to a lack of time.