Loader factory function doesn't use `MethodRepository` or `module_path` params

This is something to be aware of if there's any discussions around where new loaders should be put (if that is ever a thing, to add new loaders to httomo).

Currently, the `make_loader()` function that's used to create instances of `LoaderInterface` implementors takes in
- an implementor of `MethodRepository`
- a module path

which it doesn't actually use: https://github.com/DiamondLightSource/httomo/blob/ebd18a6275886bc6e4901bb4b71f9d1760915ffc/httomo/loaders/__init__.py#L13-L54

Relevant questions are things like:
- would we ever need methods database info to create a loader (an implementor of `LoaderInterface`)
- if we have different loaders, would they all be put into one module in httomo (in which case a module path parameter may not be needed), or would different loaders potentially be split into different modules (in which case a module path parameter may be useful)