Add geth + Ethereum Wallet integration into Brave

[diracdeltas]

Steps:

1. git pull
2. npm install
3. open Brave, turn on "Ethereum Wallet" in about:preferences#extensions
4. create a wallet (or plug in your hardware wallet) and have fun

Video demo: https://youtu.be/gIS2RVq_5R4

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed. (Ask a Brave employee to help if you cannot access this document.)

Test Plan:

Reviewer Checklist:

• Request a security/privacy review as needed if one was not already requested.

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[codecov-io]

Codecov Report

Merging #13177 into master will decrease coverage by 0.22%.
The diff coverage is 37.5%.

@@            Coverage Diff             @@
##           master   #13177      +/-   ##
==========================================
- Coverage   56.18%   55.96%   -0.23%     
==========================================
  Files         279      281       +2     
  Lines       27873    27835      -38     
  Branches     4560     4566       +6     
==========================================
- Hits        15660    15577      -83     
- Misses      12213    12258      +45

Flag	Coverage Δ
#unittest	55.96% <37.5%> (-0.23%)	⬇️

Impacted Files	Coverage Δ
js/constants/settings.js	100% <ø> (ø)	⬆️
js/constants/appConfig.js	100% <ø> (ø)	⬆️
app/locale.js	35.77% <ø> (ø)	⬆️
js/constants/config.js	55.55% <ø> (ø)	⬆️
js/about/preferences.js	59.83% <0%> (+13.23%)	⬆️
app/browser/tabs.js	23.87% <0%> (-0.36%)	⬇️
app/renderer/lib/extensionsUtil.js	58.94% <75%> (+0.05%)	⬆️
app/browser/api/ledgerNotifications.js	70.95% <0%> (-4.38%)	⬇️
app/renderer/components/preferences/paymentsTab.js	71.22% <0%> (-4.22%)	⬇️
app/browser/reducers/ledgerReducer.js	44.16% <0%> (-2.77%)	⬇️
... and 20 more

[bridiver]

we don't have a good way to do state updates in extensions with redux so an ipc message is ok, but for sending messages to the browser process we should be using actions which do work in extensions

[diracdeltas]

the problem is sending the message back to the popup window, which is a browserAction popup and not in the redux appState. is there a way to get the correct webcontents in reducers using event.sender.getId() if the sender isn't a redux tab?

[diracdeltas]

closing in favor of the updated branch #14734