Replace remaining fatal-style assertions in graph/db tests with direct
testify/require helpers. This simplifies control flow and reduces
indentation by using NoError, True/False, Equal, Len, Empty, and Nil
assertions directly.
Make the reject cache version-aware so v1 and v2 policy state can be
cached independently per channel ID. Add helpers to store v1 timestamps
or v2 block heights and thread the versioned cache key through KV/SQL
store cache accesses.