accounts/external, internal/ethapi: make ext signer sign legacy

[holiman]

Ticket #23273 found a flaw where we were unable to sign legacy-transactions using the external signer, even if we're still on non-london network. That's fixed in this PR.

Additionally, I found that even when supplying all parameters, it was impossible to sign a london-transaction on an unsynched node. It's a pretty common usecase that someone wants to sign a transaction using an unsynced 'vanilla' node, providing all necessary data. Our setDefaults, however, insisted on checking the current block against the config. This PR therefore adds a case, so that if both MaxPriorityFeePerGas and MaxFeePerGas are provided, we accept them as given.

OBS This PR fixes a regression -- on current master, we are unable to sign a london-transaction unless the node is synched, which may break scenarios where geth (or clef) is used as a cold wallet.

Tests

Using clef as a backend.

Legacy tx

> eth.signTransaction({ to: a, from:a , value:1, gasPrice: 1, gas: 22000, nonce: 0} )
{
  raw: "0xf85f80018255f0948a8eafb1cf62bfbeb1741769dae1a9dd4799619201802aa0d7af07f62836a1908b423a1274731a02e673640adb9581bc869f6356397187e0a0420e1aaf99a8772db5b7b29b0ff6d420c7962ee42cbf32bde5bc2a9d9a433ae3",
  tx: {
    gas: "0x55f0",
    gasPrice: "0x1",
    hash: "0x5ad46f61b0a976aa6123088df4f2dfabc66857f34fd723637111769d929120d5",
    input: "0x",
    maxFeePerGas: null,
    maxPriorityFeePerGas: null,
    nonce: "0x0",
    r: "0xd7af07f62836a1908b423a1274731a02e673640adb9581bc869f6356397187e0",
    s: "0x420e1aaf99a8772db5b7b29b0ff6d420c7962ee42cbf32bde5bc2a9d9a433ae3",
    to: "0x8a8eafb1cf62bfbeb1741769dae1a9dd47996192",
    type: "0x0",
    v: "0x2a",
    value: "0x1"
  }
}

Access list tx:

> eth.signTransaction({ to: a, from:a , value:1, gasPrice: 1, gas: 22000, nonce: 0, accessList:[]} )
{
  raw: "0x01f8600380018255f0948a8eafb1cf62bfbeb1741769dae1a9dd479961920180c001a0c73c18d7f32900081cdd093aebf62b4ef0fdfe1a8f05241ae8fd2b4f27872d4c9f780156fa7e37b25c2dca7a990ccfd3f93f8ccfc71e3b930f55466c23cf8fe5",
  tx: {
    accessList: [],
    chainId: "0x3",
    gas: "0x55f0",
    gasPrice: "0x1",
    hash: "0xbd4075faddb50e4f98497380c4bb315b588b74039ea23450e4e0f2a98ebaf245",
    input: "0x",
    maxFeePerGas: null,
    maxPriorityFeePerGas: null,
    nonce: "0x0",
    r: "0xc73c18d7f32900081cdd093aebf62b4ef0fdfe1a8f05241ae8fd2b4f27872d4c",
    s: "0x780156fa7e37b25c2dca7a990ccfd3f93f8ccfc71e3b930f55466c23cf8fe5",
    to: "0x8a8eafb1cf62bfbeb1741769dae1a9dd47996192",
    type: "0x1",
    v: "0x1",
    value: "0x1"
  }
}

1559 tx:

> eth.signTransaction({ to: a, from:a , value:1, gas: 22000, nonce: 0, accessList:[], maxFeePerGas: 1, maxPriorityFeePerGas: 1} )
{
  raw: "0x02f862038001018255f0948a8eafb1cf62bfbeb1741769dae1a9dd479961920180c080a092c02592bdf7cf2221f7e5023169c0540bfe0e4fcadf5646f48e8d7095c5015ca025cbd2168af56145d26bcd2a3fc779fff0b7675b0986c95318d9c1423d553051",
  tx: {
    accessList: [],
    chainId: "0x3",
    gas: "0x55f0",
    gasPrice: null,
    hash: "0x8d49e0c46228caee0715940f1e7b91ef7fe4d1690a417327187178bc98e8c7a8",
    input: "0x",
    maxFeePerGas: "0x1",
    maxPriorityFeePerGas: "0x1",
    nonce: "0x0",
    r: "0x92c02592bdf7cf2221f7e5023169c0540bfe0e4fcadf5646f48e8d7095c5015c",
    s: "0x25cbd2168af56145d26bcd2a3fc779fff0b7675b0986c95318d9c1423d553051",
    to: "0x8a8eafb1cf62bfbeb1741769dae1a9dd47996192",
    type: "0x2",
    v: "0x0",
    value: "0x1"
  }
}

[fjl]

Note: I didn't test this.

[karalabe]

If I specify both maxFee and maxPriorityFee, but the priority fee is > max fee, this PR will accept it. The original code rejected it

		if args.MaxFeePerGas.ToInt().Cmp(args.MaxPriorityFeePerGas.ToInt()) < 0 {
			return fmt.Errorf("maxFeePerGas (%v) < maxPriorityFeePerGas (%v)", args.MaxFeePerGas, args.MaxPriorityFeePerGas)
		}

^this check doesn't get called any more

[karalabe]

Note: I didn't test this.

Then don't merge it