Reorganize RPC function namespacing

[mathemancer]

Problem

The namespacing of our RPC functions has already become a bit inconsistent, and sometimes misleading.

Proposed solution

Make the following changes:

old	new
database_privileges.list_direct	databases.privileges.list_direct
database_privileges.replace_for_roles	databases.privileges.replace_for_roles
database_privileges.get_self	databases.get
database_setup.create_new	databases.setup.create_new
database_setup.connect_existing	databases.setup.connect_existing
databases.list	databases.configured.list
configured_roles.add	roles.configured.add
configured_roles.delete	roles.configured.delete
configured_roles.list	roles.configured.list
configured_roles.set_password	roles.configured.set_password
schema_privileges.list_direct	schemas.privileges.list_direct
schema_privileges.replace_for_roles	schemas.privileges.replace_for_roles
servers.list	servers.configured.list
table_privileges.list_direct	tables.privileges.list_direct
table_privileges.replace_for_roles	tables.privileges.replace_for_roles

Additional context

This arose from much confusion around database_privileges.get_self, and noticing that it was getting hard to find some functionality in the current state.

I don't expect this to take more than an hour, but I need to time it when it won't disrupt other work.