[DOC-11643] New SQL++ Statements for 8.0

[rakhi-prathap]

Jira: DOC-11643

This PR adds the following new SQL++ statements.

• Users - CREATE USER, ALTER USER, DROP USER
• Groups - CREATE GROUP, ALTER GROUP, DROP GROUP
• Buckets - CREATE BUCKET, ALTER BUCKET, DROP BUCKET

It also updates two existing statements to include the keywords user/users and group/groups.

• GRANT
• REVOKE

[dhanyagowrish]

Apologies, there are several changes that were requested, that were never specified in the DOC ticket description.

Thank you for making the changes!

[simon-dew]

Sorry there are such a lot of comments. It's a big PR! This is actually very good; all of my comments are small quibbles.

[simon-dew]

@rakhi-prathap sorry, I just added a new comment to each of the new pages about the :page-status: attribute

[rakhi-prathap]

Sorry there are such a lot of comments. It's a big PR! This is actually very good; all of my comments are small quibbles.

@simon-dew Thanks for the review and sorry about the errors. I've gone through and addressed all your comments.
Do you mind taking another look to see if we're good to merge?

[simon-dew]

LGTM! 👍