Updated 2D character controller physics tests

Added new test for 2D character controller:
Character - Pixels
Functional test for pixel art related issues around KinematicBody and
RigidBody character controllers.

Adjusted existing tests and added more test cases to cover most use
cases from recent fixed issues and regressions for KinematicBody.

Added a more automated way to run all tests with checks to see which
ones failed in character controller tests.

Also fixed some minor issues with the log scrollbar.

2d/physics_tests/utils/rigidbody_controller.gd

@@ -3,6 +3,9 @@ extends RigidBody2D
 
 var _initial_velocity = Vector2.ZERO
 var _constant_velocity = Vector2.ZERO
+var _motion_speed = 400.0
+var _gravity_force = 50.0
+var _jump_force = 1000.0
 var _velocity = Vector2.ZERO
 var _on_floor = false
 var _jumping = false
@@ -22,12 +25,12 @@ func _physics_process(_delta):
 	# Handle horizontal controls.
 	if Input.is_action_pressed("character_left"):
 		if position.x > 0.0:
-			_velocity.x = -400.0
+			_velocity.x = -_motion_speed
 			_keep_velocity = false
 			_constant_velocity = Vector2.ZERO
 	elif Input.is_action_pressed("character_right"):
 		if position.x < 1024.0:
-			_velocity.x = 400.0
+			_velocity.x = _motion_speed
 			_keep_velocity = false
 			_constant_velocity = Vector2.ZERO
 
@@ -36,14 +39,14 @@ func _physics_process(_delta):
 		if not _jumping and Input.is_action_just_pressed("character_jump"):
 			# Start jumping.
 			_jumping = true
-			_velocity.y = -1000.0
+			_velocity.y = -_jump_force
 		elif not _jumping:
-			# Apply velocity when standing for floor detection.
-			_velocity.y = 10.0
+			# Reset gravity.
+			_velocity.y = 0.0
 	else:
 		# Apply gravity and get jump ready.
+		_velocity.y += _gravity_force
 		_jumping = false
-		_velocity.y += 50.0
 
 	linear_velocity = _velocity