v2.2.0 (#3139)

## Proposed Changes

Cut release v2.2.0 including proposer boost.

## Additional Info

I also updated the clippy lints for the imminent release of Rust 1.60, although LH v2.2.0 will continue to compile using Rust 1.58 (our MSRV).

common/lighthouse_version/src/lib.rs

@@ -16,7 +16,7 @@ pub const VERSION: &str = git_version!(
         // NOTE: using --match instead of --exclude for compatibility with old Git
         "--match=thiswillnevermatchlol"
     ],
-    prefix = "Lighthouse/v2.1.5-",
+    prefix = "Lighthouse/v2.2.0-",
     fallback = "unknown"
 );