[network_info_plus_macos] more info

[alexbatalov]

Description

This PR adds missing submask, broadcast, and gateway addresses on macOS. Also fixed some indentation issues in NetworkInfoPlusPlugin.swift (was a mixture of 2 and 4 spaces). The getDefaultGateway function is a Swift port from C implementation found in getgateway.c in iOS counterpart, which probably requires some attribution to original author.

Related Issues

#501

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. Updating the pubspec.yaml and changelogs is not required.

• 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.
• 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.

[mhadaily]

@alexbatalov some checks failing.

[alexbatalov]

I think that's because CI is incorrectly configured for checking pub dependencies. It tries to run flutter pub get in all example apps without bootstrapping, which means changes in desktop implementations are not connected to example. So, if I do not increase dependency of main package on desktop package, it will effectively check example against main package (including any changes because it's dependency specified in example via path) and current versions of desktop packages downloaded from pub, thus ignoring any changes. And if I do increase dependency like I did in this PR, the check fails, because there are no such version in pub yet.

[miquelbeltran]

Thanks for the contribution @alexbatalov ! I have published the packages already