Use "essentials" SR package by default when creating environment, remove reference to `sr cluster enable`

[brianstrauch]

Release Notes

Breaking Changes

• PLACEHOLDER

New Features

• PLACEHOLDER

Bug Fixes

• Default to "Essentials" Stream Governance package in confluent environment create

Checklist

• [x] Leave this box unchecked if features are not yet available in production

What

As title suggests

References

Test & Review

Integration tests