sql: do not use raw index for count

Currently, we use raw index for count operation instead of
`box_index_count`. As a result, we skip a check if current transaction
can continue and we don't begin transaction in engine if needed. So, if
count statement is the first in a transaction, it won't be tracked by
MVCC since it wasn't notified about the transaction. The commit fixes
the mistake. Also, the commit adds a check if count was successful and
covers it with a test.

In order to backport the commit to 2.11, space name was wrapped with
quotes since it is in lower case and addressing such spaces with SQL
without quotes is Tarantool 3.0 feature. Another unsupported feature is
prohibition of data access in transactional triggers - it was used in a
test case so it was rewritten.

Closes #10825

NO_DOC=bugfix

(cherry picked from commit 0656a9231149663a0f13c4be7466d4776ccb0e66)