Per-API cost tables and the votable HookGasPrice move to the HookFeeV3
branch. V2 charges one cost unit per wasm instruction and 100 units per
hook API call (including _g), with ten units per drop rounded up.
- Guard.h: drop the per-import cost map, charge a fixed api_call_cost on
every import call
- Remove sfHookGasPrice, FeeSettings/SetFee/validation fields, fee voting,
server_info output and the hook_gas_price config knob
- hookCostToFee no longer depends on the ledger view
- Restore genesis ledger, jtx Env and fragile-hash tests to dev
- Update expected hook costs in SetHook_test