v1.5.0 rc.0 (#2506)

## Issue Addressed

NA

## Proposed Changes

- Bump to `v1.5.0-rc.0`.
- Increase attestation reprocessing queue size (I saw this filling up on Prater).
- Reduce error log for full attn reprocessing queue to warn.

## TODO

- [x] Manual testing
- [x] Resolve https://github.com/sigp/lighthouse/pull/2493
- [x] Include https://github.com/sigp/lighthouse/pull/2501

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/v1.4.0-",
+    prefix = "Lighthouse/v1.5.0-rc.0-",
     fallback = "unknown"
 );