feat(share_plus): Added excludedActivityTypes support for the iOS platform.

[StanleyCocos]

The iOS platform is missing the exclusion feature. This PR adds the platform exclusion functionality for iOS.

fix: #3377

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I titled the PR using Conventional Commits.
• I did not modify the CHANGELOG.md nor the plugin version in pubspec.yaml files.
• All existing and new tests are passing.
• The analyzer (flutter analyze) does not report any problems on my PR.

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 that with a ! in the title as explained in Conventional Commits).
• No, this is not a breaking change.

[miquelbeltran]

Thanks for this contribution as well! We have to keep this one on hold because I plan to refactor the share() method parameters, as also discussed in #3307 (comment)

Your input on this topic would be appreciated as well.

[StanleyCocos]

@miquelbeltran
Thank you for your reply.
I understand your plan now. If needed, I can still improve this PR after your plan.