Send hostname option to webtorrent to mitigate DNS rebinding

[diracdeltas]

fix #12616

complicated test plan:

system setup

1. in /etc/hosts or your system equivalent, add this entry so that brave.site is mapped to localhost: 127.0.0.1 brave.site
2. write the following to a file named index.html:

<div id='result'></div>
<script>
    const PORT = '58501' // replace this with $PORT number from later steps
    const serverUrl = `http://brave.site:${PORT}/0`
    fetch(serverUrl).then((response) => {
      response.text().then((text) => result.innerText = text)
    })
</script>

3. in the directory where index.html is located, start a local HTTP server on port 8000 using python -m SimpleHTTPServer 8000 or equivalent
4. in your Brave directory, edit js/webtorrent/entry.js to change origin: window.location.origin to origin: '*' (this helps simulate a DNS rebinding attack)

testing the PR

1. start the browser
2. go to https://webtorrent.io/torrents/sintel.torrent and click the 'start torrent' button
3. open devtools and inspect one of the download buttons to get the localhost port that the download is served from
4. replace $PORT in index.html with the port number you just found
5. now go to localhost:8000 in the browser
6. the page should appear blank

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 #13844 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #13844      +/-   ##
==========================================
- Coverage   56.53%   56.52%   -0.02%     
==========================================
  Files         283      283              
  Lines       28817    28817              
  Branches     4777     4777              
==========================================
- Hits        16293    16289       -4     
- Misses      12524    12528       +4

Flag	Coverage Δ
#unittest	56.52% <ø> (-0.02%)	⬇️

Impacted Files	Coverage Δ
app/browser/api/ledger.js	62.43% <0%> (-0.18%)	⬇️

[feross]

LGTM! 💪

[diracdeltas]

master / 0.24.x: ab89ff0