Fix proxy slowdown with intercepted HTTPS requests

[flotwig]

• Closes Network requests taking a long time to complete #6659

User facing changelog

• Fixed a regression introduced in v3.8.3 where HTTPS requests could experience slowdown.

Additional details

• in 3.5.0 Error: write EPROTO 3343909432:error:100000f0:SSL routines:OPENSSL_internal:UNSUPPORTED_PROTOCOL:../../third_party/boringssl/src/ssl/handshake_client.cc:569: #5446, we set the TLS minimum version to TLSv1
• however, this also caused slowdowns in the proxy, which are visible in the server-performance-specs if you look before and after this got merged
• all intercepted (not passthru) HTTPS connections were affected
• this PR makes it so that minVersion is set to TLSv1 only if the initial connection failed with a TLS version mismatch error
• this PR also fixes the proxy_performance_spec
  • previously, the heuristics it was using were way too loose, and also easy to misunderstand
  • now, it's as simple as "our proxy should never be more than 3x as slow as regular Chrome, under any conditions"
  • 4.5x for the case where our proxy goes through another HTTPS upstream proxy
• also noticed that requests that used an HTTPS upstream were slower - after adding setNoDelay(true), they are slightly faster, though not as fast as requests with an HTTP upstream

How has the user experience changed?

• faster for everyone,
• except for people who use TLSv1 - but they're in for a reckoning anyways when Chrome 81 and Firefox 74 deprecate their TLSv1 support: https://portswigger.net/daily-swig/tls-1-0-1-1-end-of-life-countdown-heads-into-the-danger-zone
  • this will result in 1 more socket retry per TLSv1 connection. however, Cypress keeps HTTPS sockets alive, so this is only an upfront cost and is not paid on every single request

PR Tasks

• Have tests been added/updated?
• Has the original issue been tagged with a release in ZenHub?
• [na] Has a PR for user-facing changes been opened in cypress-documentation?
• [na] Have API changes been updated in the type definitions?
• [na] Have new configuration options been added to the cypress.schema.json?

[cypress-bot]

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PR Review Checklist

If any of the following requirements can't be met, leave a comment in the review selecting 'Request changes', otherwise 'Approve'.

User Experience

• The feature/bugfix is self-documenting from within the product.
• The change provides the end user with a way to fix their problem (no dead ends).

Functionality

• The code works and performs its intended function with the correct logic.
• Performance has been factored in (for example, the code cleans up after itself to not cause memory leaks).
• The code guards against edge cases and invalid input and has tests to cover it.

Maintainability

• The code is readable (too many nested 'if's are a bad sign).
• Names used for variables, methods, etc, clearly describe their function.
• The code is easy to understood and there are relevant comments explaining.
• New algorithms are documented in the code with link(s) to external docs (flowcharts, w3c, chrome, firefox).
• There are comments containing link(s) to the addressed issue (in tests and code).

Quality

• The change does not reimplement code.
• There's not a module from the ecosystem that should be used instead.
• There is no redundant or duplicate code.
• There are no irrelevant comments left in the code.
• Tests are testing the code’s intended functionality in the best way possible.

Internal

• The original issue has been tagged with a release in ZenHub.

[cypress]

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Test summary

6966 • 0 • 97 • 0

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Run details

Project	cypress
Status	Passed
Commit	7c7a0ed
Started	Mar 11, 2020 9:11 PM
Ended	Mar 11, 2020 9:18 PM
Duration	06:49 💡
OS	Linux Debian - 10.0
Browser	Multiple

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[flotwig]

Used this script to play with minVersion outside of Cypress:

/* eslint-disable no-console */
const _ = require('lodash')
const Bluebird = require('bluebird')
const rp = require('request-promise')
const { Agent } = require('https')

const test = async () => {
  await Bluebird.delay(500)

  let agent = new Agent({ keepAlive: false })

  console.time('making 100 https requests')
  await Bluebird.all(_.times(100, async () => {
    await rp('https://weeny.chary.us/static/5MB.zip', { agent, gzip: false })
  }))

  console.timeEnd('making 100 https requests')

  await Bluebird.delay(500)

  agent = new Agent({ keepAlive: false })
  agent.createConnection = function (options, cb) {
    options.minVersion = 'TLSv1'
    cb(null, Agent.prototype.createConnection.call(agent, options))
  }

  console.time('making 100 https requests with minVersion = TLSv1')
  await Bluebird.all(_.times(100, async () => {
    await rp('https://weeny.chary.us/static/5MB.zip', { agent, gzip: false })
  }))

  console.timeEnd('making 100 https requests with minVersion = TLSv1')
}

Bluebird.mapSeries(_.times(1), test)