MSSQL

[ZBXNEXT-8672] implement metric handlers

* commit '01cee58e8592699364d0e2bda96e4363bc4f77ae':
  [ZBXNEXT-8672] fix close dbcons unit test
  [ZBXNEXT-8672] change last.backup.get metric column name
  [ZBXNEXT-8672] add unit tests
  [ZBXNEXT-8672] fix commented issues
  [ZBXNEXT-8672] implement metric handlers