feat!: renamed package `geocoding_ios` to `geocoding_darwin`

[OutdatedGuy]

Renames geocoding_ios to geocoding_darwin to later add macOS support. Will follow up with macOS support PR after this is merged.

resolves #244

Pre-launch Checklist

• [x] I made sure the project builds.
• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [x] I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is does not need version changes.
• [x] I updated CHANGELOG.md to add a description of the change.
• [ ] I updated/added relevant documentation (doc comments with ///).
• [ ] I rebased onto main.
• [ ] I added new tests to check the change I am making, or this PR does not need tests.
• [x] I made sure all existing and new tests are passing.
• [x] I ran dart format . and committed any changes.
• [x] I ran flutter analyze and fixed any errors.