RustCrypto crate upgrades; MSRV 1.57 (#378)

Updates all of the RustCrypto dependencies to the latest versions:

- `des` v0.8
- `elliptic-curve` v0.12
- `hmac` v0.12
- `num-bigint-dig` v0.8
- `pbkdf2` v0.11
- `p256` v0.11
- `p384` v0.10
- `rsa` v0.6
- `sha1` v0.10 (replacing `sha-1`)
- `sha2` v0.10

src/piv.rs

@@ -57,8 +57,10 @@ use log::{debug, error, warn};
 use p256::NistP256;
 use p384::NistP384;
 use rsa::{BigUint, RsaPublicKey};
-use std::fmt::{Display, Formatter};
-use std::str::FromStr;
+use std::{
+    fmt::{Display, Formatter},
+    str::FromStr,
+};
 
 #[cfg(feature = "untested")]
 use {