AP_Scripting: add test for require() after rescheduling

It can end up broken due to incorrect assumptions about the executed
function's upvalues, which might change after rescheduling.

libraries/AP_Scripting/tests/scripting_require_test_2.lua

@@ -0,0 +1,35 @@
+-- main require tests are in scripting_test.lua
+
+-- DO NOT EDIT!!!! it's very easy to make this accidentally pass even when the
+-- original problem is still present!! we do some very careful work to check
+-- that require works even when the function's first upvalue is not the script
+-- environment.
+
+local loop_time = 500 -- number of ms between runs
+
+-- need to shadow gcs to make the upvalues right
+local gcs = gcs -- luacheck: ignore
+
+local passes = 0 -- run both before and after scheduling
+
+local require_global = require("test/nested")
+
+local function update()
+   -- need to send before requiring to make the upvalues right
+  gcs:send_text(6, "testing")
+  local require_local = require("test/nested") -- should not crash
+
+  -- validate we got the same object (object contents validated in main test)
+  if require_local == require_global then
+    passes = passes + 1
+  else
+    gcs:send_text(0, "Failed: require returned different objects")
+  end
+  if passes >= 3 then
+    gcs:send_text(3, "Require test 2 passed")
+  end
+
+  return update, loop_time
+end
+
+return update() -- run immediately before starting to reschedule