vinyl: do not abort unrelated transactions on DDL

Since commit 8f4be322 ("txm: disallow yields after DDL operation in
TX"), any DDL operation aborts **all** active transactions, even those
that wouldn't be affected by it anyway, see `memtx_engine_prepare()`,
`memtx_tx_abort_all_for_ddl()`. Actually, there's no need to do that in
Vinyl because it properly handles concurrent DDL operations, see commit
d3e12369 ("vinyl: abort affected transactions when space is removed
from cache"). Let's skip Vinyl transactions from consideration by
marking the Vinyl engine with a special flag.

Closes #10375

NO_DOC=bug fix

(cherry picked from commit f5f061d051dc6268949bfcb141d211142282578d)