ETH transfer fixes and sweep ETH addition

[dimalinux]

• Fixes problems with the existing ETH transfer method
• Allows transfers to contracts or regular account address
• Adds a sweep ETH feature that's symmetric to the existing XMR sweep feature
• Provides unit tests to existing and new code

[codecov[bot]]

Codecov Report

Patch coverage: 67.04% and project coverage change: +2.20 :tada:

Comparison is base (0f1865c) 58.68% compared to head (ad63820) 60.88%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #481 +/- ## ========================================== + Coverage 58.68% 60.88% +2.20% ========================================== Files 128 129 +1 Lines 12608 12787 +179 ========================================== + Hits 7399 7786 +387 + Misses 4452 4185 -267 - Partials 757 816 +59 ``` | [Impacted Files](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [ethereum/erc20\_token.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-ZXRoZXJldW0vZXJjMjBfdG9rZW4uZ28=) | `10.90% <0.00%> (-0.18%)` | :arrow_down: | | [protocol/xmrtaker/instance.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-cHJvdG9jb2wveG1ydGFrZXIvaW5zdGFuY2UuZ28=) | `44.55% <0.00%> (+24.67%)` | :arrow_up: | | [rpc/server.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-cnBjL3NlcnZlci5nbw==) | `75.39% <ø> (ø)` | | | [rpcclient/ws\_methods.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-cnBjY2xpZW50L3dzX21ldGhvZHMuZ28=) | `54.16% <0.00%> (ø)` | | | [tests/ganache.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-dGVzdHMvZ2FuYWNoZS5nbw==) | `80.00% <ø> (ø)` | | | [cmd/swapcli/util.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y21kL3N3YXBjbGkvdXRpbC5nbw==) | `56.43% <40.00%> (-4.06%)` | :arrow_down: | | [cliutil/utils.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y2xpdXRpbC91dGlscy5nbw==) | `58.59% <42.85%> (+1.45%)` | :arrow_up: | | [rpc/personal.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-cnBjL3BlcnNvbmFsLmdv) | `64.55% <66.66%> (+20.11%)` | :arrow_up: | | [ethereum/extethclient/transfer.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-ZXRoZXJldW0vZXh0ZXRoY2xpZW50L3RyYW5zZmVyLmdv) | `68.42% <68.42%> (ø)` | | | [rpcclient/personal.go](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-cnBjY2xpZW50L3BlcnNvbmFsLmdv) | `59.30% <70.00%> (+32.98%)` | :arrow_up: | | ... and [7 more](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | | ... and [11 files with indirect coverage changes](https://app.codecov.io/gh/AthanorLabs/atomic-swap/pull/481/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.