### 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)

Vector<TileSetPlugin *> get_tile_set_atlas_plugins() const;
	
	
	void set_tile_shape(TileShape p_shape);
	TileShape get_tile_shape() const;
	void set_tile_layout(TileLayout p_layout);
	TileLayout get_tile_layout() const;
	void set_tile_offset_axis(TileOffsetAxis p_alignment);
	TileOffsetAxis get_tile_offset_axis() const;
	void set_tile_size(Size2i p_size);
	Size2i get_tile_size() const;
	
	int get_next_source_id() const;
	int get_source_count() const;
	int get_source_id(int p_index) const;
	int add_source(Ref<TileSetSource> p_tile_set_source, int p_source_id_override = -1);
	void set_source_id(int p_source_id, int p_new_id);
	void remove_source(int p_source_id);
	bool has_source(int p_source_id) const;
	Ref<TileSetSource> get_source(int p_source_id) const;
	
	void set_uv_clipping(bool p_uv_clipping);
	bool is_uv_clipping() const;
	int get_occlusion_layers_count() const;
	void add_occlusion_layer(int p_index = -1);
	void move_occlusion_layer(int p_from_index, int p_to_pos);
	void remove_occlusion_layer(int p_index);
	void set_occlusion_layer_light_mask(int p_layer_index, int p_light_mask);
	int get_occlusion_layer_light_mask(int p_layer_index) const;
	void set_occlusion_layer_sdf_collision(int p_layer_index, bool p_sdf_collision);