Wayback machine feature should be disabled in Tor windows or use Tor

[diracdeltas]

Problem

As reported in https://bravesoftware.slack.com/archives/C85NV6NSG/p1582256790113900 (see thread), we found that clicking the "Checked for saved version" button on a 404 page in a Tor window will send a request to https://brave-api.archive.org/... that doesn't go through Tor. As such, this is a privacy problem.

Expected behavior

1. open a Tor window
2. go to https://brave.com/dfkdfjd
3. either you should not see a notification bar that offers to check the Wayback machine or you should see this, and clicking on the button to check the Wayback machine does not issue a request that goes over plain TLS. (check for it in a request inspector like Wireshark)

What about private windows?

I think this feature is probably ok to keep in private windows because it uses a network context that doesn't store state on disk (https://cs.chromium.org/chromium/src/chrome/browser/net/system_network_context_manager.h?q=systemnetwork&sq=package:chromium&g=0&l=44-45) and we disallow cookies (https://github.com/brave/brave-core/pull/3561/files#diff-306f17e629f5adfd7444084d21b89193R38) for it.

However if the fix is easier to do with it disabled entirely in private windows (Tor windows included), I am pro doing that.

underlying cause

The system network context (https://github.com/brave/brave-core/pull/3561/files#diff-6d51337a3d8e25d0c3fbb40ef046dce9R58) doesn't use the Tor window proxy setting.

[GeetaSarvadnya]

Verification passed on

Brave	1.4.96 Chromium: 80.0.3987.132 (Official Build) (64-bit)
Revision	fcea73228632975e052eb90fcf6cd1752d3b42b4-refs/branch-heads/3987@{#974}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Issue Reproducible in 1.4.95 wherein https://brave-api.archive.org/ is being listed in Fiddler network monitoring tool request/response
  
• Verified the test plan from Make wayback url request to use per-profile SharedLoaderFactory brave-core#4763
• Verified that click on http://www.brave.com/bo-> Check for saved version displays the archived page in TOR
• Verified that https://brave-api.archive.org/ isn't being displayed in fiddler in 1.4.96
  

Verification passed on

Brave	1.4.96 Chromium: 80.0.3987.132 (Official Build) (64-bit)
Revision	fcea73228632975e052eb90fcf6cd1752d3b42b4-refs/branch-heads/3987@{#974}
OS	Ubuntu 18.04 LTS

• Verified the test plan from Make wayback url request to use per-profile SharedLoaderFactory brave-core#4763
• Verified that click on https://brave.com/dfkdfjd-> Check for saved version displays the archived page in TOR
• Verified that Brave does not connect tohttps://brave-api.archive.org/
  

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Verified passed with

Brave	1.4.96 Chromium: 80.0.3987.132 (Official Build) (64-bit)
Revision	fcea73228632975e052eb90fcf6cd1752d3b42b4-refs/branch-heads/3987@{#974}
OS	macOS Version 10.14.6 (Build 18G3020)

• Reproduced the issue using 1.4.95 - https://brave-api.archive.org/ is listed in Charles when using Tor window:

• Verified the test plan from Make wayback url request to use per-profile SharedLoaderFactory brave-core#4763, https://brave-api.archive.org/ is not listed in Charles when using Tor window:

• Verified STR from description