* Add fuzzer for the compact custom codec implementation introduced in PR #6720.

This commit adds a fuzzing harness for the custom compact encoding/decoding
introduced in PR #6720.

* Update primitives/npos-elections/fuzzer/src/compact.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update Cargo.lock: Add changes in elections-fuzzer

* Change indentation from spaces to tabs

Co-authored-by: Vincent Ulitzsch <vincent@srlabs.de>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>