### Godot version

3.5 (991bb6ac7) -> 4.0.beta10 (d0398f62f)

### System information

Windows 11

### Issue description

I have some relatively simple tilesets created in version 3.5 containing textures, collision shapes, and occlusion polygons. These tilesets are almost completely unusable when migrated into Godot 4 without recreating most of the tileset by hand. Specifically:

- Tile size seems to always be set at 16x16 (this might be the root cause of some of the other issues). This might not be easy to convert properly since tile size is a property of the TileMap in Godot 3, but of the TileSet in Godot 4. That being said, the converter could likely guess at the proper tile size based on the tiles present in the map (e.g. given that all my tiles are 32x32, it would be logical to set tile size as 32x32).
- No occlusion layer is created, meaning **all occlusion polygons are lost**.
- Collision polygons are incorrectly offset from the textures: ![image](https://user-images.githubusercontent.com/4420888/210156434-90331901-5e1c-4f16-9839-19a21bbcc5d9.png) (this wouldn't be as big of a deal if there was a way to "drag" entire collision polygons rather than just individual vertices, but it seems like to only way to fix them is to recreate them from scratch).
- Collision polygons aren't rotated properly in auto-generated rotation alt tiles:
![image](https://user-images.githubusercontent.com/4420888/210156473-069cc7c4-3466-4aba-83ff-693dbba31737.png)
- (I imagine these same issues are present for tileset navigation layers, but I haven't tested that)

Probably related to issues #64006 and #67218.

### Steps to reproduce

- Create a basic tileset with occlusion + collision polygons in Godot 3.
- Convert the project to a Godot 4 project.
- Open the project in 4 and pay attention to the Tileset's textures & collision/occlusion polygons.


### Minimal reproduction project

[convert4.zip](https://github.com/godotengine/godot/files/10328029/convert4.zip)

bool get_flip_v() const;
	void set_transpose(bool p_transpose);
	bool get_transpose() const;
	void set_texture_origin(Vector2i p_texture_origin);
	Vector2i get_texture_origin() const;
	void set_material(Ref<Material> p_material);
	Ref<Material> get_material() const;
	void set_modulate(Color p_modulate);
	Color get_modulate() const;
	void set_z_index(int p_z_index);
	int get_z_index() const;
	void set_y_sort_origin(int p_y_sort_origin);
	int get_y_sort_origin() const;
	void set_occluder(int p_layer_id, Ref<OccluderPolygon2D> p_occluder_polygon);
	Ref<OccluderPolygon2D> get_occluder(int p_layer_id) const;
	
	void set_constant_linear_velocity(int p_layer_id, const Vector2 &p_velocity);
	Vector2 get_constant_linear_velocity(int p_layer_id) const;
	void set_constant_angular_velocity(int p_layer_id, real_t p_velocity);
	real_t get_constant_angular_velocity(int p_layer_id) const;
	void set_collision_polygons_count(int p_layer_id, int p_shapes_count);
	int get_collision_polygons_count(int p_layer_id) const;
	void add_collision_polygon(int p_layer_id);
	void remove_collision_polygon(int p_layer_id, int p_polygon_index);
	void set_collision_polygon_points(int p_layer_id, int p_polygon_index, Vector<Vector2> p_polygon);
	Vector<Vector2> get_collision_polygon_points(int p_layer_id, int p_polygon_index) const;
	void set_collision_polygon_one_way(int p_layer_id, int p_polygon_index, bool p_one_way);
	bool is_collision_polygon_one_way(int p_layer_id, int p_polygon_index) const;
	void set_collision_polygon_one_way_margin(int p_layer_id, int p_polygon_index, float p_one_way_margin);
	float get_collision_polygon_one_way_margin(int p_layer_id, int p_polygon_index) const;