FROMGIT: rust: alloc: add Vec::pop

This introduces a basic method that our custom Vec is missing. I expect
that it will be used in many places, but at the time of writing, Rust
Binder has six calls to Vec::pop.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250502-vec-methods-v5-2-06d20ad9366f@google.com


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

Bug: 414994413
(cherry picked from commit f2b4dd70
 https://github.com/Rust-for-Linux/linux.git

 alloc-next)
Change-Id: I81085d4a5fc7fe9377c3857e8f0adca8aabd8984
Signed-off-by: Alice Ryhl <aliceryhl@google.com>