[FIX] migration bug

Trying to setup a six nodes chain with Native RUNE , I discovered a bug which left 0.000375 BNB behind. Also there are a small amount BTC on a retiring vault , which block vault churning to finish.

Root cause for BNB is because we changed the migration logic to ignore RUNE , yet forget to exclude RUNE for gas calculation.

Root cause for BTC is we allow signer to use fee rate and spend less gas.