Ability to remove alternative fee swap path for account without ED

[xlc]

Followup of #1730, need to check if there are storages on Karura for dusted accounts and have a signed tx to wipe those storage.

[zqhxuyuan]

script:

const paths = await api.query.transactionPayment.alternativeFeeSwapPath.keys();
const accounts = await paths.map(({ args: [accountId] }) => accountId);
const balances = accounts.forEach(async (account) => {
  let data = await api.query.system.account(account);
  if(data.data.free == 0) {
    console.log(account);
  }
});

result:

oSfNzvA2J2UYEnFuba8ja6L5GWUa6BhB1iwj2e59qYQt8jG
rvQwKpV9kDdU2aK58yHa1x6rkVpP8c9Cdj5QTE2VJ3LfPia
sy1cgqqAMSpho1j7ANf8ghyKMwdYY4dDBHHbkoXvGbSXGqt
oXVCj5UFVSc1gW2zCCEZaXXPyzjAqwsPCcVx2MCfimnGAEC
rM1NqhffLAAGPoUSiRWD4Ybn26QFRKkSxPahfuzWKWVCv2S
tWaQAB8c9HQ2y3guCPqDFwVfRouLAHS4b4yYQwYkL2rTfx9
rfGbq3RfuxDYW9YuReu4DhsMrooNwrHcx97t5QUuPmndMpF
u1dP8F3VB2AMDLyAgEyKqaMXQ4K2ou3TJL5FEE8TDd3dJuw
qtwKGTjmauoztdUcRjJ42pPYkJR1WWXPYSzpPhHYEwUpX6r
r5XX5tvHKsKc9sdnaENaMxGrU4smGzMJB6bnU5LWHkgd1ov
tW3QFYuJjP6NYqanyVxf4FK9X4k1n6FnQxuoyfPs7dmvFy1
rhyLQPzr7xWvzDV1dBEN27Az1fJFU1A98Z6wqjhNYkMeWdV
txU88EidXVVYHWoxAdgwCAXfodQRXDK8ta6NrqT1zBwRPtz
pMYiPQM5oLigXbjCwSsS7sDHJgKjYA1mDtZDZuej73VL5Bq
svRXX4NF5aDzCQYRFwsQ6TfYkhd1Xcs8pmBuXKwuJtBgRvA
qtJFmxRapWPKXM6VGXcmxRnNdUyX7cFdEFyuQpJEtufzZ41

not too much.