give example test explorer debug configurations hidden presentation (#4397)

`${cmake.testProgram}` is only valid in debug launch configurations when
they are run from the Test Explorer. Configurations that use it always
fail with "'${cmake.testProgram}' does not exist" when run from the Run
and Debug sidebar. Recommend hiding them to remove a source of errors.

Author: malsyned

Diff for: docs/debug-launch.md

@@ -207,6 +207,7 @@ A couple of examples:
     "name": "(ctest) Launch",
     "type": "cppdbg",
     "request": "launch",
+    "presentation": { "hidden": true },
     // Resolved by CMake Tools:
     "cwd": "${cmake.testWorkingDirectory}",
     "program": "${cmake.testProgram}",
@@ -219,6 +220,7 @@ A couple of examples:
     "name": "(ctest) Launch",
     "type": "cppvsdbg",
     "request": "launch",
+    "presentation": { "hidden": true },
     // Resolved by CMake Tools:
     "program": "${cmake.testProgram}",
     "args": [ "${cmake.testArgs}"],