ci: target 2019.4 LTS, 2020.3 LTS, 2021.1 TECH, 2021.2 TECH and trunk versions (#628)

* ci: target 2019.4 LTS, 2020.3 LTS, 2021.1, 2021.2 and trunk versions

* fixed lifecycle v2 version order

Co-authored-by: Matt Walsh <matt.walsh@unity3d.com>

Author: 0xFA11

.yamato/project.metafile

@@ -1,7 +1,12 @@
 # Editors where tests will happen. The first entry of this array is also used
-# for validation
+# for validation.
+#
+# Therefore, **do not** put an older V1-lifecycle ver. 
+#  like 2020.x or 2019.x on top of 'test_editors'
 test_editors:
   - 2021.1
+  - 2021.2
+  - 2020.3
   - 2019.4
   - trunk