Replace unmaintained directories crate

Fixes RUSTSEC-2020-0054 warning from cargo-audit/cargo-deny, follows the recommendation to switch to the new maintained `directories-next` crate fork

Only affects the cache directory determination for the environment and was a simple search'n'replace to this fork so don't think behavior has changed.

https://rustsec.org/advisories/RUSTSEC-2020-0054

crates/cache/Cargo.toml

@@ -12,7 +12,7 @@ edition = "2018"
 anyhow = "1.0"
 base64 = "0.12.0"
 bincode = "1.1.4"
-directories = "2.0.1"
+directories-next = "1.0"
 file-per-thread-logger = "0.1.1"
 log = { version = "0.4.8", default-features = false }
 serde = { version = "1.0.94", features = ["derive"] }

crates/cache/src/config.rs

@@ -2,7 +2,7 @@
 
 use super::Worker;
 use anyhow::{anyhow, bail, Context, Result};
-use directories::ProjectDirs;
+use directories_next::ProjectDirs;
 use log::{trace, warn};
 use serde::{
     de::{self, Deserializer},