Bump lru from 0.7.8 to 0.8.0 (#6060)

* Bump lru from 0.7.8 to 0.8.0

Bumps [lru](https://github.com/jeromefroe/lru-rs) from 0.7.8 to 0.8.0.
- [Release notes](https://github.com/jeromefroe/lru-rs/releases)
- [Changelog](https://github.com/jeromefroe/lru-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jeromefroe/lru-rs/compare/0.7.8...0.8.0)

---
updated-dependencies:
- dependency-name: lru
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

* Change `LruCache` paramerter to `NonZeroUsize`

* Change type of `session_cache_lru_size` to `NonZeroUsize`

* Add expects instead of unwrap

Co-authored-by: Bastian Köcher <info@kchr.de>

* Use match to get rid of expects

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Sebastian Kunert <skunert49@gmail.com>
Co-authored-by: Bastian Köcher <info@kchr.de>

polkadot/node/overseer/src/lib.rs

@@ -62,6 +62,7 @@
 use std::{
 	collections::{hash_map, HashMap},
 	fmt::{self, Debug},
+	num::NonZeroUsize,
 	pin::Pin,
 	sync::Arc,
 	time::Duration,
@@ -112,7 +113,10 @@ pub use orchestra::{
 
 /// Store 2 days worth of blocks, not accounting for forks,
 /// in the LRU cache. Assumes a 6-second block time.
-pub const KNOWN_LEAVES_CACHE_SIZE: usize = 2 * 24 * 3600 / 6;
+pub const KNOWN_LEAVES_CACHE_SIZE: NonZeroUsize = match NonZeroUsize::new(2 * 24 * 3600 / 6) {
+	Some(cap) => cap,
+	None => panic!("Known leaves cache size must be non-zero"),
+};
 
 #[cfg(test)]
 mod tests;