sql: raise an error on attempt to use HASH index in SQL

Since currently query planner is unable to use HASH indexes
and attempt to use it will likely lead to SEGFAULT, this
patch raises an error on attempt to open VDBE cursor
against HASH index.

@TarantoolBot document
Title: Doceument allowed index type for SQL
Before the change, Tarantool query planner segfaulted on
try of using non-tree index. It is blocked now w/ appropriate
error message. Need to document the behaviour.
It should be noted, that this restriction might be relaxed in future.

Closes #4659