[url_launcher] Removed reference to rootViewController during initialization

[vitor-gyant]

Description

The current plugin implementation stores a reference to the rootViewController during the initialisation which breaks scenarios like app2app. This PR does not store any variable to rootViewController but search through the VC hierarchy to get the top most VC in order to present the new vc.

Related Issues

flutter/flutter#33259

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth and quick review process.

• 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.

[cyanglaz]

LGTM overall

[vitor-gyant]

@cyanglaz Let me know if there is anything pending to merge the PR on my side. thanks!

[cyanglaz]

Left one comment. And also the CI doesn't seem to be happy, could you fix it as well?

[vitor-gyant]

@cyanglaz I have fixed code format and changed the parameter name. I'm not able to understand why build_all_plugins fails. It seems that name is missing from the pubspec but I didn't remove it. Could you help me on this ? Thanks

[vitor-gyant]

@cyanglaz Sorry for pushing this but it would be great to have this merged. I'm happy to fix the build_all_plugins issue if you can help me figure out what is the underlying problem. Thanks.

[mklim]

Sorry about that @vitor-gyant. Looking through it I think this was a bug unrelated to this PR that has been since fixed on master. If you merge master in it should be resolved.

[mklim]

Sorry, there's been another breakage since then in flutter/flutter that's currently turning CI red now. It will be green again once flutter/flutter#40282 lands.

[vitor-gyant]

@mklim Thanks it now works perfectly. Looking forward for the merge :)

[vitor-gyant]

@mklim Thank you!

[mklim]

@vitor-gyant thank you for the contribution!