Port ClassDB tests to use doctest

Extracted the most minimal core initialization functionality from
`setup()` and `setup2()` so that `ClassDB` could be tested properly
(input, audio, rendering, physics etc, are excluded).

Display and rendering servers/singletons are not initialized at all.

Due to the fact that most subsystems are disabled, fixed various crashes in the
process (in order):
- `AcceptDialog` OK/cancel swap behavior (used `DisplayServer` while
  `register_scene_types()`);
- `make_default_theme` which depends on `RenderingServer`;
- `XRServer` singleton access while calling `register_modules_types()`;
- hidden bug in a way joypads are cleaned up (MacOS and Linux only).

Removed manual `ClassDB` init/cleanup calls from `test_validate_testing.h`.

ClassDB tests:

Co-authored-by: Ignacio Etcheverry <ignalfonsore@gmail.com>

1 files changed, 0 insertions, 4 deletions

diff --git a/tests/test_validate_testing.h b/tests/test_validate_testing.h
index 4bcc57d9c5..b4ea6eb576 100644
--- a/tests/test_validate_testing.h
+++ b/tests/test_validate_testing.h
@@ -54,8 +54,6 @@ TEST_SUITE("Validate tests") {
 		CHECK_MESSAGE(_print_error_enabled, "Error printing should be re-enabled.");
 	}
 	TEST_CASE("Stringify Variant types") {
-		ClassDB::init(); // For objects.
-
 		Variant var;
 		INFO(var);
 
@@ -185,8 +183,6 @@ TEST_SUITE("Validate tests") {
 				<< var << " " << vec2 << " " << rect2 << " " << color);
 
 		CHECK(true); // So all above prints.
-
-		ClassDB::cleanup();
 	}
 }