Remove unused Bullet module and thirdparty code

It has been disabled in `master` since one year (godotengine#45852) and our plan
is for Bullet, and possibly other thirdparty physics engines, to be
implemented via GDExtension so that they can be selected by the users
who need them.

COPYRIGHT.txt

@@ -130,11 +130,6 @@ Comment: Basis Universal
 Copyright: 2019, Binomial LLC.
 License: Apache-2.0
 
-Files: ./thirdparty/bullet/
-Comment: Bullet Continuous Collision Detection and Physics Library
-Copyright: 2003-2013, Erwin Coumans
-License: Zlib
-
 Files: ./thirdparty/certs/ca-certificates.crt
 Comment: CA certificates
 Copyright: Mozilla Contributors

SConstruct

@@ -198,7 +198,6 @@ opts.Add("system_certs_path", "Use this path as SSL certificates default for edi
 opts.Add(BoolVariable("use_precise_math_checks", "Math checks use very precise epsilon (debug option)", False))
 
 # Thirdparty libraries
-opts.Add(BoolVariable("builtin_bullet", "Use the built-in Bullet library", True))
 opts.Add(BoolVariable("builtin_certs", "Use the built-in SSL certificates bundles", True))
 opts.Add(BoolVariable("builtin_embree", "Use the built-in Embree library", True))
 opts.Add(BoolVariable("builtin_enet", "Use the built-in ENet library", True))

core/config/project_settings.cpp

@@ -1236,9 +1236,6 @@ ProjectSettings::ProjectSettings() {
 	custom_prop_info["rendering/driver/threads/thread_model"] = PropertyInfo(Variant::INT, "rendering/driver/threads/thread_model", PROPERTY_HINT_ENUM, "Single-Unsafe,Single-Safe,Multi-Threaded");
 	GLOBAL_DEF("physics/2d/run_on_separate_thread", false);
 	GLOBAL_DEF("physics/3d/run_on_separate_thread", false);
-	// Required to make the project setting appear even if the physics engine is GodotPhysics,
-	// while also making it appear in the ProjectSettings class documentation.
-	GLOBAL_DEF("physics/3d/smooth_trimesh_collision", false);
 
 	GLOBAL_DEF("debug/settings/profiler/max_functions", 16384);
 	custom_prop_info["debug/settings/profiler/max_functions"] = PropertyInfo(Variant::INT, "debug/settings/profiler/max_functions", PROPERTY_HINT_RANGE, "128,65535,1");

doc/classes/ProjectSettings.xml

@@ -1493,7 +1493,7 @@
 		</member>
 		<member name="physics/3d/physics_engine" type="String" setter="" getter="" default="&quot;DEFAULT&quot;">
 			Sets which physics engine to use for 3D physics.
-			"DEFAULT" is currently the [url=https://bulletphysics.org]Bullet[/url] physics engine. The "GodotPhysics3D" engine is still supported as an alternative.
+			"DEFAULT" and "GodotPhysics3D" are the same, as there is currently no alternative 3D physics server implemented.
 		</member>
 		<member name="physics/3d/run_on_separate_thread" type="bool" setter="" getter="" default="false">
 			If [code]true[/code], the 3D physics server runs on a separate thread, making better use of multi-core CPUs. If [code]false[/code], the 3D physics server runs on the main thread. Running the physics server on a separate thread can increase performance, but restricts API access to only physics process.
@@ -1504,10 +1504,6 @@
 		<member name="physics/3d/sleep_threshold_linear" type="float" setter="" getter="" default="0.1">
 			Threshold linear velocity under which a 3D physics body will be considered inactive. See [constant PhysicsServer3D.SPACE_PARAM_BODY_LINEAR_VELOCITY_SLEEP_THRESHOLD].
 		</member>
-		<member name="physics/3d/smooth_trimesh_collision" type="bool" setter="" getter="" default="false">
-			If [code]true[/code], smooths out collision with trimesh shapes ([ConcavePolygonShape3D]) by telling the Bullet physics engine to generate internal edge information for every trimesh shape created.
-			[b]Note:[/b] Only effective if [member physics/3d/physics_engine] is set to [code]Bullet[/code], [i]not[/i] [code]DEFAULT[/code] or [code]GodotPhysics[/code].
-		</member>
 		<member name="physics/3d/solver/contact_max_allowed_penetration" type="float" setter="" getter="" default="0.01">
 			Maximum distance a shape can penetrate another shape before it is considered a collision. See [constant PhysicsServer3D.SPACE_PARAM_CONTACT_MAX_ALLOWED_PENETRATION].
 		</member>

doc/classes/RigidDynamicBody3D.xml

@@ -227,7 +227,6 @@
 				[code]body[/code] the [Node], if it exists in the tree, of the other [PhysicsBody3D] or [GridMap].
 				[code]body_shape_index[/code] the index of the [Shape3D] of the other [PhysicsBody3D] or [GridMap] used by the [PhysicsServer3D]. Get the [CollisionShape3D] node with [code]body.shape_owner_get_owner(body.shape_find_owner(body_shape_index))[/code].
 				[code]local_shape_index[/code] the index of the [Shape3D] of this RigidDynamicBody3D used by the [PhysicsServer3D]. Get the [CollisionShape3D] node with [code]self.shape_owner_get_owner(self.shape_find_owner(local_shape_index))[/code].
-				[b]Note:[/b] Bullet physics cannot identify the shape index when using a [ConcavePolygonShape3D]. Don't use multiple [CollisionShape3D]s when using a [ConcavePolygonShape3D] with Bullet physics if you need shape indices.
 			</description>
 		</signal>
 		<signal name="body_shape_exited">
@@ -241,7 +240,6 @@
 				[code]body[/code] the [Node], if it exists in the tree, of the other [PhysicsBody3D] or [GridMap].
 				[code]body_shape_index[/code] the index of the [Shape3D] of the other [PhysicsBody3D] or [GridMap] used by the [PhysicsServer3D]. Get the [CollisionShape3D] node with [code]body.shape_owner_get_owner(body.shape_find_owner(body_shape_index))[/code].
 				[code]local_shape_index[/code] the index of the [Shape3D] of this RigidDynamicBody3D used by the [PhysicsServer3D]. Get the [CollisionShape3D] node with [code]self.shape_owner_get_owner(self.shape_find_owner(local_shape_index))[/code].
-				[b]Note:[/b] Bullet physics cannot identify the shape index when using a [ConcavePolygonShape3D]. Don't use multiple [CollisionShape3D]s when using a [ConcavePolygonShape3D] with Bullet physics if you need shape indices.
 			</description>
 		</signal>
 		<signal name="sleeping_state_changed">