Provide optional Read/Write methods for stdio

[thaliaarchi]

The raw types for standard I/O across platforms vary by which of the optional io::Read and io::Write methods they provide and most just use the defaults. Only Unix implements read_buf, read_vectored, and write_vectored for its stdio. Provide these methods for the platforms which support them or when useful. Additionally, provide missing methods for StdinRaw, StdoutLock, and StderrLock, which the other similar types provide.

I have checked the code against a target per platform modified, with wasm32-unknown-unknown for unsupported stdio, as well as Linux, macOS, and Windows.

x check library/std --target=aarch64-apple-darwin
x check library/std --target=aarch64-kmc-solid_asp3
x check library/std --target=aarch64-unknown-linux-gnu
x check library/std --target=aarch64-unknown-teeos
x check library/std --target=riscv32im-risc0-zkvm-elf
x check library/std --target=riscv32imac-unknown-xous-elf
x check library/std --target=wasm32-unknown-unknown
x check library/std --target=wasm32-wasip1
x check library/std --target=x86_64-fortanix-unknown-sgx
x check library/std --target=x86_64-pc-windows-gnu
x check library/std --target=x86_64-unknown-hermit
x check library/std --target=x86_64-unknown-uefi

Progress on optional Read/Write methods is tracked in #136756.

Later work

Windows and UEFI stdio use UTF-16, so will take more work to flesh out. I plan to refactor the WTF-8 abstraction from OsStr to accommodate this in a future PR.

[rustbot]

r? @Noratrieb

rustbot has assigned @Noratrieb.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[thaliaarchi]

@joboet Looks like you wrote #136780 to have minimum conflicts to this. Thanks for that. I don't mind rebasing onto that, if yours is merged first.

[Noratrieb]

r? joboet

[thaliaarchi]

I dropped a few commits from this PR:

• 5da7fbe (Fix unsafe_op_in_unsafe_fn for TEEOS), because Apply unsafe_op_in_unsafe_fn to the standard library #136986 is in the merge queue
• 1a08321 (Deduplicate unsupported fs.rs for UEFI) per Nora's note
• 1b05019 (Remove unused methods on Hermit FileDesc), because that would be a better fit for a file-focused PR.

[thaliaarchi]

Since this touches a lot of targets, I'm going to split this into multiple PRs for more target-focused review, once #136780 goes through the merge queue.

[joboet]

Since this touches a lot of targets, I'm going to split this into multiple PRs for more target-focused review, once #136780 goes through the merge queue.

That'd be great, thank you! Especially the SGX stuff would be much simpler to review as a dedicated PR.

[thaliaarchi]

@rustbot blocked (on #136780)