Rollup merge of #137107 - thaliaarchi:io-optional-methods/cursors, r=joboet

Override default `Write` methods for cursor-like types

Override the default `io::Write` methods for cursor-like types to provide more efficient versions.

Writes to resizable containers already write everything, so implement `write_all` and `write_all_vectored` in terms of those. For fixed-sized containers, cut out unnecessary error checking and looping for those same methods.

| `impl Write for T`              | `vectored` | `all` | `all_vectored` | `fmt`   |
| ------------------------------- | ---------- | ----- | -------------- | ------- |
| `&mut [u8]`                     | Y          | Y     | new            |         |
| `Vec<u8>`                       | Y          | Y     | new            | #137762 |
| `VecDeque<u8>`                  | Y          | Y     | new            | #137762 |
| `std::io::Cursor<&mut [u8]>`    | Y          | new   | new            |         |
| `std::io::Cursor<&mut Vec<u8>>` | Y          | new   | new            | #137762 |
| `std::io::Cursor<Vec<u8>>`      | Y          | new   | new            | #137762 |
| `std::io::Cursor<Box<[u8]>>`    | Y          | new   | new            |         |
| `std::io::Cursor<[u8; N]>`      | Y          | new   | new            |         |
| `core::io::BorrowedCursor<'_>`  | new        | new   | new            |         |

Tracked in https://github.com/rust-lang/rust/issues/136756.

# Open questions

Is it guaranteed by `Write::write_all` that the maximal write is performed when not everything can be written? Its documentation describes the behavior of the default implementation, which writes until a 0-length write is encountered, thus implying that a maximal write is expected. In contrast, `Read::read_exact` declares that the contents of the buffer are unspecified for short reads. If it were allowed, these cursor-like types could bail on the write altogether if it has insufficient capacity.

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