Update schema request with kafka env

[muralibasani]

Linked issue

Resolves: #1593

What kind of change does this PR introduce?

• Bug fix
• New feature
• Refactor
• Docs update
• CI update

What is the current behavior?

Describe the state of the application before this PR. Illustrations appreciated (videos, gifs, screenshots).
To submit a schema request, currently schema environment is passed in for environment parameter.

What is the new behavior?

Describe the state of the application after this PR. Illustrations appreciated (videos, gifs, screenshots).

• To submit a schema request, kafka environment is passed in for environment parameter. This allows us to remove unnecessary call to get schema environments list api, and keeps it unique to promotion of schema too
• Deletes an api getEnvsForSchemaRequests
• In Angular : removed topic and env selection in schema request form

Other information:

Additional changes, explanations of the approach taken, unresolved issues, necessary follow ups, etc.

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)

[muralibasani]

@programmiri I think we need FE changes here

[aindriu-aiven]

LGTM
I also tested this locally creating a new schema and had no issue with the environment assignement.

[aindriu-aiven]

Finished testing it, was unable to fully test the promotion aspect due to issues with my environment but both angular and React crated new requests correctly with the Kafka environment Id

[programmiri]

🎉 We still should wait for Mathieu to do a review for the frontend changes.