Update the UpsertChannelPolicy query to apply different staleness
checks based on gossip version. For v1 policies, continue checking
last_update timestamps. For v2 policies, check block_height instead,
using >= comparison to handle policies from the same block.
The version-specific WHERE clause ensures that policy updates are only
applied when they contain newer information according to the versioning
scheme appropriate for that gossip version.
Elle Mouton
677e6ea89c