Secrets Management page needs improvement

1. In the opening section there is discussion about protecting secrets and then it mentions the use of a password for encrypting secrets, but there is no mention of what the secrets are. Basically it isn't clear why I would want to use this feature since I'm not sure exactly what it is helping to protect.

2. There is no mention that this is an optional feature that can be used and also no mention that it is EE only. Both of these should be mentioned in the first 1-2 paragraphs or at least towards the top of the page.

3. Some things in the password rotation settings are not clear. For example, I'm not sure what the data key rotation is or how I would do it. What does it mean to rotate the data key? Secret rotation seems like changing the admin password. Why isn't it just called "Changing the admin password"? Same thing with rotating the master password. Are we rotating it or just changing it?

4. In the examples section it should be noted that you must run the couchbase-cli commands on the same node that the server is on.

5. (A minor note) The image of how secret management works in the first section feels like it was dropped in. At least for me I don't feel that it helped me grasp how secret management works. We can probably improve this image or even add in a section lower down explaining the implementation details.