Add import from perfstats scripts for dm_os_schedulers

need to modify TextRowsets.xml to add

<Rowset name="tbl_dm_os_schedulers" enabled="true" identifier="-- dm_os_schedulers --" type="RowsetImportEngine.TextRowset">
  <Column name="rownum" type="RowsetImportEngine.BigIntColumn" length="24" valuetoken="ROWNUMBER" />
  <Column name="runtime" type="RowsetImportEngine.DateTimeColumn" />    
  <Column name="scheduler_address" type="RowsetImportEngine.VarBinaryColumn"  />
  <Column name="parent_node_id" type="RowsetImportEngine.IntColumn" />
  <Column name="scheduler_id" type="RowsetImportEngine.IntColumn" />
  <Column name="cpu_id" type="RowsetImportEngine.IntColumn" />
  <Column name="status" type="RowsetImportEngine.NVarCharColumn" length="40"  />
  <Column name="is_online" type="RowsetImportEngine.IntColumn" />
  <Column name="is_idle" type="RowsetImportEngine.IntColumn" />
  <Column name="preemptive_switches_count" type="RowsetImportEngine.BigIntColumn" />
  <Column name="context_switches_count" type="RowsetImportEngine.BigIntColumn" />
  <Column name="idle_switches_count" type="RowsetImportEngine.BigIntColumn" />
  <Column name="current_tasks_count" type="RowsetImportEngine.IntColumn" />
  <Column name="runnable_tasks_count" type="RowsetImportEngine.IntColumn" />
  <Column name="current_workers_count" type="RowsetImportEngine.IntColumn" />
  <Column name="active_workers_count" type="RowsetImportEngine.IntColumn" />
  <Column name="work_queue_count" type="RowsetImportEngine.IntColumn" />
  <Column name="pending_disk_io_count" type="RowsetImportEngine.IntColumn" />
  <Column name="load_factor" type="RowsetImportEngine.IntColumn" />
  <Column name="yield_count" type="RowsetImportEngine.BigIntColumn" />
  <Column name="last_timer_activity" type="RowsetImportEngine.BigIntColumn" />
  <Column name="failed_to_create_worker" type="RowsetImportEngine.IntColumn" />
  <Column name="active_worker_address" type="RowsetImportEngine.VarBinaryColumn" />
  <Column name="memory_object_address" type="RowsetImportEngine.VarBinaryColumn" />
  <Column name="task_memory_object_address" type="RowsetImportEngine.VarBinaryColumn" />
  <Column name="quantum_length_us" type="RowsetImportEngine.IntColumn" />
  <Column name="total_cpu_usage_ms" type="RowsetImportEngine.BigIntColumn" />
  <Column name="total_cpu_idle_capped_ms " type="RowsetImportEngine.BigIntColumn" />
  <Column name="total_scheduler_delay_ms " type="RowsetImportEngine.BigIntColumn" />
</Rowset> 

to be able to import the scheduler information collected in perfstats script.

Locate TextRowsets.xml and compare its existing Rowset entries with the supplied tbl_dm_os_schedulers definition. Add the rowset needed to import scheduler information collected by the perfstats script, then verify that the XML remains valid and the scheduler data can be imported.