rust: module: add type `LocalModule`

The `LocalModule` type is the type of the module created by `module!`,
`module_pci_driver!`, `module_platform_driver!`, etc.

Since the exact type of the module is sometimes generated on the fly by
the listed macros, provide an alias.

This is first used by the `module_firmware!` macro.

Acked-by: Miguel Ojeda <ojeda@kernel.org>
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250306222336.23482-2-dakr@kernel.org


Signed-off-by: Danilo Krummrich <dakr@kernel.org>