feat: EXPOSED-334 Support MERGE statement

[obabichevjb]

This PR introduces a new mergeFrom method query method, allowing execute underlying sql merge command. The merge method supports merging data from one table or select query into another table, with conditional logic for matched and unmatched rows.

The method can be used in the following way:

Dest.mergeFrom(Source, on = { Source.key eq Dest.key() }) {
  whenNotMatchedInsert {
      it[Dest.key] = Source.key
      it[Dest.value] = Source.value
  }

  whenMatchedDelete(and = (Source.value eq 1))

  whenMatchedUpdate(and = (Source.value eq 1)) {
      it[Dest.key] = Source.key
      it[Dest.value] = (Dest.value + Source.value) * 10
  }
}

Merge command is supported by the databases: SQL Server, Postgres, Oracle, H2

[e5l]

Please update the PR description

[obabichevjb]

Please update the PR description

Updated