password-hash: remove Display/FromStr bounds on Params (#2212)

For the associated type `CustomizedPasswordHasher::Params`, removes the
`Display` and `FromStr` bounds which aren't actually used: for
PHC-related purposes which are the only ones implemented directly in
`password-hash`, it instead requires a `TryFrom<phc::ParamsString>` impl
instead.

Requiring these as well seemed like good hygiene so there's some way to
serialize and parse the params as a string, but it becomes a problem
when the params are shared between e.g. PHC and MCF implementations
where each of them has a different params serialization so there's not
one "true" serialization for which it actually makes sense to impl
`Display` and `FromStr`.

Author: tarcieri

password-hash/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "password-hash"
-version = "0.6.0-rc.9"
+version = "0.6.0-rc.10"
 authors = ["RustCrypto Developers"]
 edition = "2024"
 rust-version = "1.85"

password-hash/src/lib.rs

@@ -56,10 +56,7 @@ pub type PasswordHash = phc::PasswordHash;
 #[allow(deprecated)]
 pub type PasswordHashString = phc::PasswordHashString;
 
-use core::{
-    fmt::{Debug, Display},
-    str::FromStr,
-};
+use core::fmt::Debug;
 
 #[cfg(feature = "rand_core")]
 use rand_core::TryCryptoRng;
@@ -122,7 +119,7 @@ pub trait PasswordHasher<H> {
 /// Generic around a password hash to be returned (typically [`PasswordHash`])
 pub trait CustomizedPasswordHasher<H> {
     /// Algorithm-specific parameters.
-    type Params: Clone + Debug + Default + Display + FromStr;
+    type Params: Clone + Debug + Default;
 
     /// Compute a [`PasswordHash`] from the provided password using an
     /// explicit set of customized algorithm parameters as opposed to the