rust: irq: add support for non-threaded IRQs and handlers

rust: irq: add support for non-threaded IRQs and handlers

This patch adds support for non-threaded IRQs and handlers through
irq::Registration and the irq::Handler trait.

Registering an irq is dependent upon having a IrqRequest that was
previously allocated by a given device. This will be introduced in
subsequent patches.

Tested-by: Joel Fernandes <joelagnelf@nvidia.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250811-topics-tyr-request_irq2-v9-3-0485dcd9bcbf@collabora.com
[ Remove expect(dead_code) from Flags::into_inner(), add
  expect(dead_code) to IrqRequest::new(), fix intra-doc links. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>