FROMGIT: rust: alloc: add Vec::remove

This is needed by Rust Binder in the range allocator, and by upcoming
GPU drivers during firmware initialization.

Panics in the kernel are best avoided when possible, so an error is
returned if the index is out of bounds. An error type is used rather
than just returning Option<T> to let callers handle errors with ?.

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-v5-6-06d20ad9366f@google.com


[ Remove `# Panics` section; `Vec::remove() handles the error properly.`
  - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Bug: 414994413
(cherry picked from commit 294a7ecb
 https://github.com/Rust-for-Linux/linux.git

 alloc-next)
Change-Id: I80a8925910f234cccd325614634aa8a12e85ea1c
Signed-off-by: Alice Ryhl <aliceryhl@google.com>