Implements a very basic backtrace and the ability to format them
If you run the panic example and press A, you get:
```
[ERROR] GBA Debug: [failed]
[ERROR] GBA Debug: debug data: ce3-1ee7-1fb7-24d-1ad
[FATAL] GBA Debug: Error: panicked at src/memory_mapped.rs:101:24:
index out of bounds: the len is 240 but the index is 240
```
which you can then prettify with:
```
> agb-addr2line ../target/thumbv4t-none-eabi/debug/examples/panic 0ce3-1f57-2027-024d-01ad
0: rust_begin_unwind <agb>/lib.rs:321
1: core::panicking::panic_nounwind <core>/panicking.rs:151
2: core::panicking::assert_failed_inner <core>/panicking.rs:321
3: agb::memory_mapped::MemoryMapped2DArray<T,_,_>::set <agb>/memory_mapped.rs:101
(inlined by) agb::display::bitmap3::Bitmap3::draw_point <agb>/display/bitmap3.rs:31
4: main /home/gwilym/Projects/agb/agb/examples/panic.rs:15
```
- [ ] Changelog updated / no changelog update needed
* A redesign of objects giving the option of a more managed and an
unmanaged system.
* Managed system features
* Z ordering (should be efficient, based on a doubly linked list).
* More than 128 objects if some are disabled (not currently efficient).
* Unmanaged
* Same sprite system as before.
* You control how objects get put in to OAM with the unmanaged OAM.
TODO before this is mergable:
* [x] Docs pass, aim for everything to have docs as before.
* [x] Tests, some of these needs some run time testing.
* [x] Affine matrices, I'm not leaving this to die this time.
* [x] Some API redo, so the names make sense / are similar to before.
Future work:
* The Sprite loader should keep most recently used sprites around and
upon allocation of a new sprite try unloading the least recently used
sprite. (Performance wise this would be a disaster as it would be doing
dealloc and alloc in vblank, so really we want to "learn" how much
buffer we should maintain and try to get that during GC).
- [x] Changelog updated