Tool to publish tombstones for a subject

# What is currently missing?

A tool to help cleanup the `_schemas` topic without having to go over the REST API

# How could this be improved?

Write the tool. It should:

- Read the existing `_schemas`
- For each entry
- If it is a schema of the matching subject, then publish a tombstone entry with the same key
- After all entries had the tombstone record published
- Change the topic's configuration to speed up compaction
- Monitor the topic and wait for the data to be compacted. Report to the user progress.

# Is this a feature you would work on yourself?

[ ] I plan to open a pull request for this feature