fix metadata disable full scan

[famarting]

The changes in this PR address, but don't fix directly, this issues:

• Bug: cluster admin refresh medatadata report error when set Metadata.Full to false. #2069
• backgroundMetadataUpdater can log ErrNoTopicsToUpdateMetadata repetitively if client.conf.Metadata.Full is false #2630

Also this will be of great help in Dapr: dapr/components-contrib#3247

With this changes now it will be possible to set config.Metadata.Full = false but it would require the user to set a topic via
config.Metadata.InitialTopics = []string{"dummy-topic"} , with this the first request to fetch the metadata will either create that topic if it doesn't exist or it will just fetch its metadata

[github-actions]

Thank you for your contribution! However, this pull request has not had any activity in the past 90 days and will be closed in 30 days if no updates occur.
If you believe the changes are still valid then please verify your branch has no conflicts with main and rebase if needed. If you are awaiting a (re-)review then please let us know.

[famarting]

ping, is there any interest in this contribution? I'm happy to debate it further or change anything that is needed