[Feature Request] Skip formatting doc comments altogether when mixing sugared and de-sugared doc comments

Input:

//! <details open>
//!     <summary>Example 1</summary>
//!
//! ```
#![doc = "test()"]
//! ```
//!
//! </details>
//!
//! <details open>
//!     <summary>Example 2</summary>
//!
//! ```
//! example(2);
//! ```
//!
//! </details>

rustfmt +nightly --config format_code_in_doc_comments=true

Outputs:

//! <details open>
//!     <summary>Example 1</summary>
//!
//! ```
#![doc = "test()"]
//! ```
//!
//! </details>
//!
//! <details open>
//!     <summary>Example 2</summary>
//! ```
//! example(2);
//! ```
//!
//! </details>

Note no empty line before second example. So rustdoc of output looks like this:

Empty lines before backticks are important for Markdown.

Rustdoc uses commonmark

HTML blocks in commonmark must end with empty line:

End condition: line is followed by a blank line

rustfmt 1.7.0-nightly (ca663b06 2024-01-08)

Reproduce the issue with the shown rustfmt nightly command and input, then trace the doc-comment formatting path. Add a regression test covering mixed sugared and de-sugared comments, with the expected output preserving the blank line before the second fenced block.