Make `pallet-bridge-rewards` generic over `RewardKind` #20508

Job	Run time
check-dependency-rules	8s
check-workspace	20s
check-fail-ci	11s
check-markdown	16s
check-readme	3m 12s
preflight / preflight	47s
preflight / ci-versions	1m 3s
check-umbrella	2m 9s
check-rust-feature-propagation	2m 2s
check-toml-format	1m 1s
fmt	1m 10s
test-rust-features	2m 2s
All quick checks passed	1s
	14m 22s

Provide feedback