Both normalize_doc_attributes and wrap_comments require an unstable toolchain

The formatting options used by the cargo install version (https://github.com/oxidecomputer/progenitor/blob/main/cargo-progenitor/src/main.rs#L94) use formatting options that are documented as unstable:

• https://rust-lang.github.io/rustfmt/?version=v1.7.1&search=#normalize_comments
• https://rust-lang.github.io/rustfmt/?version=v1.7.1&search=#wrap_comments

RUST_BACKTRACE=1 cargo progenitor -i api-definition.yml -o output -n output -v 0.1.0
-----------------------------------------------------
 TYPE SPACE
-----------------------------------------------------
....
-----------------------------------------------------

thread 'main' panicked at /Users/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/cargo-progenitor-0.7.0/src/main.rs:101:68:
called `Result::unwrap()` on an `Err` value: Unstable("wrap_comments, normalize_doc_attributes")
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: cargo_progenitor::reformat_code
   4: cargo_progenitor::main

Start in cargo-progenitor/src/main.rs around the formatting options at line 94 and reformat_code near line 101. Reproduce the failure with the cargo progenitor command shown in the issue using a stable toolchain, then trace how the unstable options are applied. Done means the command no longer panics because of normalize_doc_attributes or wrap_comments and generated output remains formatted.