[devscripts/run_tests] Use markers to filter tests (#1258)

`-k` filters using a substring match on test name.
`-m` checks markers for an exact match.
Authored by: sulyi

devscripts/run_tests.bat

@@ -3,11 +3,11 @@
 cd /d %~dp0..
 
 if ["%~1"]==[""] (
-    set "test_set="
+    set "test_set="test""
 ) else if ["%~1"]==["core"] (
-    set "test_set=-k "not download""
+    set "test_set="-m not download""
 ) else if ["%~1"]==["download"] (
-    set "test_set=-k download"
+    set "test_set="-m "download""
 ) else (
     echo.Invalid test type "%~1". Use "core" ^| "download"
     exit /b 1