box: add sql grant object type

Closes #8803

@TarantoolBot document
Title: Document `lua_eval`, `lua_call`, and `sql` grant object types

In Tarantool 3.0 we introduced the new `lua_eval`, `lua_call`, and `sql`
object types for `box.schema.user.grant` to control access to code
execution over the network protocol (IPROTO).

1. Granting the 'execute' privilege on `lua_eval` permits the user to
   execute arbitrary Lua code with the `IPROTO_EVAL` request.

   Example:

   ```Lua
   box.cfg({listen = 3301})
   box.schema.user.create('alice', {password = 'secret'})
   conn = require('net.box').connect(
       box.cfg.listen, {user = 'alice', password = 'secret'})
   conn:eval('return true') -- access denied
   box.schema.user.grant('alice', 'execute', 'lua_eval')
   conn:eval('return true') -- ok
   ```

2. Granting the 'execute' privilege on `lua_call` permits the user to
   call any global (accessible via the `_G` Lua table) user-defined
   Lua function with the `IPROTO_CALL` request. It does **not** permit
   the user to call built-in Lua functions, such as `loadstring` or
   `box.session.su`. It does **not** permit the user to call functions
   registered in the `_func` system space with `box.schema.func.create`
   (access to those functions is still controlled by privileges granted
   on `function`).

   Example:

   ```Lua
   function my_func() end
   box.cfg({listen = 3301})
   box.schema.user.create('alice', {password = 'secret'})
   conn = require('net.box').connect(
       box.cfg.listen, {user = 'alice', password = 'secret'})
   conn:call('my_func') -- access denied
   box.schema.user.grant('alice', 'execute', 'lua_call')
   conn:call('my_func') -- ok
   conn:call('box.session.su', {'admin'}) -- access denied
   ```

3. Granting the 'execute' privilege on `sql` permits the user to
   execute an arbitrary SQL expression with the `IPROTO_PREPARE`
   and `IPROTO_EXECUTE` requests. Without this privilege or the
   'execute' privilege granted on `universe`, the user is **not**
   permitted to execute SQL expressions over IPROTO anymore.
   Note that before Tarantool 3.0 any user (even guest) could execute
   SQL expressions over IPROTO. It is possible to revert to the old
   behavior by toggling the `sql_priv` compat option. Please add
   a description to https://tarantool.io/compat/sql_priv

   Example:

   ```Lua
   box.cfg({listen = 3301})
   box.schema.user.create('alice', {password = 'secret'})
   conn = require('net.box').connect(
       box.cfg.listen, {user = 'alice', password = 'secret'})
   conn:execute('SELECT 1') -- access denied
   box.schema.user.grant('alice', 'execute', 'sql')
   conn:execute('SELECT 1') -- ok
   ```