rust: hrtimer: introduce hrtimer support

Add support for intrusive use of the hrtimer system. For now,
only add support for embedding one timer per Rust struct.

The hrtimer Rust API is based on the intrusive style pattern introduced by
the Rust workqueue API.

Acked-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://lore.kernel.org/r/20250309-hrtimer-v3-v6-12-rc2-v12-1-73586e2bd5f1@kernel.org


Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>