build: intergrate fuzz crate into workspace

This makes `fuzz` use the same lockfile
as the rest of the crates
and makes sure it fuzzes the same versions
of dependencies, e.g. `mailparse`.

src/fuzzing.rs

@@ -1,12 +0,0 @@
-//! # Fuzzing module.
-//!
-//! This module exposes private APIs for fuzzing.
-
-/// Fuzzing target for simplify().
-///
-/// Calls simplify() and panics if simplify() panics.
-/// Does not return any value to avoid exposing internal crate types.
-#[cfg(fuzzing)]
-pub fn simplify(input: String, is_chat_message: bool) {
-    crate::simplify::simplify(input, is_chat_message);
-}

src/lib.rs

@@ -116,6 +116,3 @@ pub const DCC_MIME_DEBUG: &str = "DCC_MIME_DEBUG";
 mod test_utils;
 #[cfg(test)]
 mod tests;
-
-#[cfg(fuzzing)]
-pub mod fuzzing;