Add getAllSchemas command

[calindima]

I didn't create an issue but I can if that's necessary, otherwise I'll write the details in this PR.

Motivation

Explain here the context, and why you're making that change. What is the problem you're trying to solve.

We have a use case where we want to query the SchemaRegistry to retrieve a history of schema versions and observe schema evolution for topics with higher retention (e.g. infinite retention, >6mo retention etc.).

Modifications

Describe the modifications you've done.

The PR only contains additions such as:

• Added a new file for getAllSchemas command which retrieves all schemas of a topic and pretty prints them
• Added a helper method to pretty print the schema list
• Added a call to register the new command
• Added a test

I'm not completely sure if adding a new command was the way to go, so I'm open to suggestions for alternatives (e.g. as a flag to the get command)

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• Added a test to check the output of the new command

Documentation

Check the box below.

Need to update docs?

I'm actually not sure if there are any docs I should update, very open to feedback on this one.

• doc-required

  (If you need help on updating docs, create a doc issue)

• no-need-doc

  (Please explain why)

• doc

  (If this PR contains doc changes)

[github-actions]

@calindima:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)

[calindima]

I'll remove this and change the version once apache/pulsar-client-go#1289 is released