Fix Camera 2D position not updating correctly

[madmiraal]

Currently, SceneTree's initial physics_process_time and process_time are set to 1 second. So early calls to get_process_delta_time() or get_physics_process_delta_time() return unreasonably large values, which causes incorrect calculations. Most notably in Camera2D's initial position when smoothing is enabled:

godot/scene/2d/camera_2d.cpp

Lines 158 to 161 in 5a6b13b

	if (smoothing_enabled && !Engine::get_singleton()->is_editor_hint()) {
	real_t c = smoothing * (process_callback == CAMERA2D_PROCESS_PHYSICS ? get_physics_process_delta_time() : get_process_delta_time());
	smoothed_camera_pos = ((camera_pos - smoothed_camera_pos) * c) + smoothed_camera_pos;
	ret_camera_pos = smoothed_camera_pos;

In addition, when a Camera2D's limits are updated, the camera's position is not updated. This is requiring users to unnecessarily, manually call the hidden _update_scroll() method.

This PR fixes both these issues by setting SceneTree's initial process times to 0 and calling _update_scroll() when setting limits. It also fixes scene_tree.h's clang formatting, required to make changes to scene_tree.h and a TestEdit test that depends on SceneTree's initial process times being arbitrarily greater than 0.

Fixes #56336
Fixes #56913

[akien-mga]

Thanks!