Update wp_stream_get_sites() to work consistently with the limit/number argument

[dd32]

Update wp_stream_get_sites() to work consistently with the limit/number argument

This also changes it so that by default, list every site rather than the first 100 encountered on networks.

This also changes it to listing all sites by default, rather than only the first 100.

Checklist

• Project documentation has been updated to reflect the changes in this pull request, if applicable.
• I have tested the changes in the local development environment (see contributing.md).
• I have added phpunit tests.

Release Changelog

• Fix: Describe a bug fix included in this release.
• New: Describe a new feature in this release.

Release Checklist

• This pull request is to the master branch.
• Release version follows semantic versioning. Does it include breaking changes?
• Update changelog in readme.txt.
• Bump version in stream.php.
• Bump Stable tag in readme.txt.
• Bump version in classes/class-plugin.php.
• Draft a release on GitHub.

Change [ ] to [x] to mark the items as done.

[kasparsd]

Thanks for the pull request @dd32, it looks good!

Is this ready to be merged?