docs: rust: extend abstraction and binding documentation

Add some basics explained by Miguel in [1] to the documentation.
And connect it with some hints where this is implemented in the
kernel.

Link: https://www.linuxfoundation.org/webinars/rust-for-linux-writing-abstractions-and-drivers

 [1]
Cc: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20240418070618.3962736-1-dirk.behme@de.bosch.com


[ Reworded first section for better clarity and some minor nits.
  Changed link into Link tag, use tabs for code block
  indentation and wrap at 80. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>