* Give `GPU2D::Unit` a virtual destructor
- Undefined behavior avoided!
* Add an `array2d` alias
* Move various parts of `GPU2D::SoftRenderer` to `constexpr`
- `SoftRenderer::MosaicTable` is now initialized at compile-time
- Most of the `SoftRenderer::Color*` functions are now `constexpr`
- The aforementioned functions are used with a constant value in at least one place, so they'll be at least partially computed at compile-time
* Generalize `GLRenderer::PrepareCaptureFrame`
- Declare it in the base `Renderer3D` class, but make it empty
* Remove unneeded `virtual` specifiers
* Store `Framebuffer`'s memory in `unique_ptr`s
- Reduce the risk of leaks this way
* Clean up how `GLCompositor` is initialized
- Return it as an `std::optional` instead of a `std::unique_ptr`
- Make `GLCompositor` movable
- Replace `GLCompositor`'s plain arrays with `std::array` to simplify moving
* Pass `GPU` to `GLCompositor`'s important functions instead of passing it to the constructor
* Move `GLCompositor` to be a field within `GLRenderer`
- Some methods were moved up and made `virtual`
* Fix some linker errors
* Set the renderer in the frontend
* Remove unneeded `virtual` specifiers
* Remove `RenderSettings` in favor of just exposing the relevant member variables
* Update the frontend to accommodate the core changes
* Add `constexpr` and `const` to places in the interpolator
* Qualify references to `size_t`
* Construct the `optional` directly instead of using `make_optional`
- It makes the Linux build choke
- I think it's because `GLCompositor`'s constructor is `private`
* Reorganize namespaces
- Most types are now moved into the `melonDS` namespace
- Only good chance to do this for a while, since a big refactor is next
* Fix the build
