Dolt SQL procedure for managing dolt_docs

We currently use the `dolt_docs` system table to manage docs via SQL. Users can directly modify this table to add, edit, and delete docs. In SQL-only contexts like Hosted users need to manually create the `dolt_docs` table to create a doc for the first time. This is a bad UI and inconsistent with other dolt features like branches, tags, commits, etc

We should make a `dolt_docs` procedure to manage docs so users don't need to create/directly modify the `dolt_docs` table and to be more consistent with other features