Update buildChanPolicy and related functions in both KV and SQL stores
to properly construct ChannelEdgePolicy with version-specific fields:
KVStore changes:
- Reject non-v1 policies in updateEdgePolicy and serializeChanEdgePolicy
since KV store only supports v1 gossip protocol.
- Set Version to GossipVersion1 when deserializing policies from KV.
SQLStore changes:
- Add isNode1 parameter to buildChanPolicy functions to properly set
SecondPeer field (v2 uses SecondPeer instead of ChannelFlags direction).
- Extract Version from database and populate version-specific fields:
- For v1: MessageFlags, ChannelFlags, LastUpdate, ExtraOpaqueData
- For v2: DisableFlags, LastBlockHeight, ExtraSignedFields
- Thread isNode1 through buildChanPolicyWithBatchData and
buildCachedChanPolicies call sites.
This enables the SQL store to read and reconstruct both v1 and v2
channel policies from the database with proper field mapping.