Add stress unit tests with several processes to config

tests/stress_tests/.automation/unittests/nightly_configs/desktop_test_config.xml

@@ -1,6 +1,10 @@
 <attributes>
     <processes>
         <value>1</value>
+        <value>2</value>
+        <value>4</value>
+        <value>8</value>
+        <value>16</value>
     </processes>
     <threads>
         <value>1</value>

tests/stress_tests/.automation/unittests/nightly_configs/myriad_test_config.xml

@@ -1,6 +1,10 @@
 <attributes>
     <processes>
         <value>1</value>
+        <value>2</value>
+        <value>4</value>
+        <value>8</value>
+        <value>16</value>
     </processes>
     <threads>
         <value>1</value>

tests/stress_tests/.automation/unittests/weekly_configs/desktop_test_config.xml

@@ -1,6 +1,10 @@
 <attributes>
     <processes>
         <value>1</value>
+        <value>2</value>
+        <value>4</value>
+        <value>8</value>
+        <value>16</value>
     </processes>
     <threads>
         <value>1</value>