test/e2e: allow overriding some browser settings via env vars

[legobeat]

Description

Allow configuring some browser behavior for local e2e testing using the following environment variables:

• Override https proxy: SELENIUM_HTTPS_PROXY
• Disable DNS-over-TLS for chromium (using system DNS): SELENIUM_DISABLE_DOT
• Enable headless mode: SELENIUM_HEADLESS

Also disables some unnecessary phoning-home to Google servers by chromium during testing.

Related issues

Fixes:

Manual testing steps

1. Create test build: yarn build:test
2. Start a local http proxy listening on e.g. 127.0.0.1:1234
3. chromium: Initiate headless e2e test with DoT disabled SELENIUM_HTTPS_PROXY=http://127.0.0.1:1234 SELENIUM_DISABLE_DOT=1 SELENIUM_HEADLESS=1 yarn test:e2e:chrome --build-type main

• observe queries hitting your proxy, tests executing with no browser window opening, and no DoT requests being made

4. firefox: Initiate headless e2e test: SELENIUM_HTTPS_PROXY=http://127.0.0.1:1234 SELENIUM_HEADLESS=1 yarn test:e2e:firefox --build-type main

• observe queries hitting your proxy, tests executing with no browser window opening

Screenshots/Recordings

Before

After

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[HowardBraham]

This is very very interesting, but I have a few questions:

• Under what circumstances would you want to override the included proxy at 127.0.0.1:8000?
• SELENIUM_HEADLESS fails on a lot of our tests, it would be nice to know why (this is not necessarily a question to Lego). Then we could maybe run headless on CircleCI.

[legobeat]

This is very very interesting, but I have a few questions:

* Under what circumstances would you want to override the included proxy at `127.0.0.1:8000`?

Might want to do some auditing, debugging, interception or what not with http calls being made. For example a local squid or mitmproxy instance. There are probably use-cases I didn't think of too ^^

* `SELENIUM_HEADLESS` fails on a lot of our tests, it would be nice to know why (this is not necessarily a question to Lego).  Then we could maybe run headless on CircleCI.

So it's not just me then...

But I have some consistent e2e test failures that happen locally on develop without any of these overrides and figuring these help in debugging situations like that locally. At this point I haven't figured out yet where the discrepancy in results locally vs circleci comes from.

[metamaskbot]

No release label on PR. Adding release label release-11.12.0 on PR, as PR was added to branch 11.12.0 when release was cut.