Filter data out from system databases for Azure SQL DB only (#8849)

* Excluding data from system databases like msdb,model which are not
relevant for monitoring in Azure SQL

Please enter the commit message for your changes. Lines starting

* Addressing review comments to handle null scenarios

plugins/inputs/sqlserver/azuresqlqueries.go

@@ -438,6 +438,10 @@ WITH PerfCounters AS (
 			ELSE d.[physical_database_name]
 		END
 	WHERE
+		/*filter out unnecessary SQL DB system database counters, other than master and tempdb*/
+		NOT (spi.object_name LIKE 'MSSQL%:Databases%' AND spi.instance_name IN ('model','model_masterdb','model_userdb','msdb','mssqlsystemresource'))
+		AND
+		(
 			counter_name IN (
 				 'SQL Compilations/sec'
 				,'SQL Re-Compilations/sec'
@@ -540,6 +544,7 @@ WITH PerfCounters AS (
 					,'Latch Waits/sec'
 				)
 			)
+		)
 )
 
 INSERT INTO @PCounters select * from PerfCounters