Update the fastlane plugin to use the BugSnag CLI

[joshedney]

Goal

Update the Fastlane plugin to delegate dSYM uploads to the BugSnag CLI, improving consistency and maintainability.

Changeset

• Added CLI support: The plugin now exposes the option to use the BugSnag CLI for dSYM uploads.
• Custom CLI path support: Users can specify a locally installed CLI binary instead of using the bundled version.
• If the provided CLI version is older than the bundled one, the plugin will raise an error with instructions to update.
• Dynamic CLI selection: Logic was added to determine the correct bundled CLI binary based on the host architecture.
• Option passthrough: Relevant options from the Fastlane plugin are now passed through to the CLI, ensuring feature parity.

Testing

• Existing tests updated to reflect CLI integration.

[tomlongridge]

We refer to this in our legacy docs along with the Homebrew install.

I don't think we should keep it, but we should think about updates to:

• the readme
• the legacy docs
• Homebrew

[tomlongridge]

How many of these tests do we no longer run? Is there good reason?

[joshedney]

These tests were all related to the bin/bugsnag-dsym-upload file, which has now been integrated into the BugSnag CLI, which has tests to cover its functionality.