Update to btcd v0.26 / v2 modules

[ziggie1984]

lnd is migrating to btcd v0.26 and the new split v2 modules:
wire/v2, txscript/v2, chaincfg/v2, chainhash/v2, btcutil/v2, psbt/v2, address/v2.

Pool is directly affected and should be updated so it can consume newer lnd and btcsuite module versions without mixing old btcd package paths with the new v2 module types.

Current impact observed on master:

• go.mod still requires old btcd modules: github.com/btcsuite/btcd/btcutil, github.com/btcsuite/btcd/btcutil/psbt, github.com/btcsuite/btcd/chaincfg/chainhash.
• go.mod currently depends on older lnd modules, including lnd v0.19.0-beta, lnd/tlv v1.3.1, and lnd/tor v1.1.6.
• 63 tracked Go files contain old btcd import paths.
• 6 tracked Go files reference moved btcutil address symbols.

Useful references:

• btcd migration script: scripts: add script to upgrade to v2 modules automatically btcsuite/btcd#2547
• lnd tlv/tor submodule update: tlv+tor: update btcd modules to v2 lightningnetwork/lnd#10902
• lnd migration commit: lightningnetwork/lnd@8047149c6
• lnd tlv/tor pseudo-version source: lightningnetwork/lnd@a067468f0f45

Expected work:

• Run/adapt the btcd v2 migration script.
• Regenerate any generated RPC/API code if needed.
• Update direct dependencies to btcd v0.26 and split v2 modules.
• Update downstream Lightning Labs deps once compatible versions exist.
• Fix manual compile issues such as address package shadowing and changed APIs.
• Run module tidy/build/test checks.