[Bug Found + Fix] Full Stack Code Coverage

# I'm submitting a ...
Bug report plus solution for improvement.

# Context
I've decided to implement the fullstack code coverage on my project which is a front Angular with back Nestjs. It's quite a big project, both in the front and the back side.
Implementation with Angular was really straightforward thank's to https://github.com/skylock/cypress-angular-coverage-example

Fullstack Implementation was simple too, but led me to some bugs. The cy.request() made during the afterAll hook which is supposed to get the __coverage__ json was failing like 9 out of 10 times (timeout error).
I quickly deduced that the size of the json sent was the problem, it's about 5mb.

I tried multiple things like, changing the response timeout to 5 minutes, sending the result compressed as gzip, or sending the json as a string, then parsing it in the front, but none of these solutions worked.

And then I saw that under the hood cy.request which is used to communicate with the backend to get the coverage json, was used with HTTP1 which is super slow.
So I found this workaround which now gets the json, in like 1 sec instead of 20sec (when it worked).

# Current implementation
> // node_modules/@cypress/code-coverage/support.js

```js
after(() => {
// there might be server-side code coverage information
// we should grab it once after all tests finish
const baseUrl = Cypress.config('baseUrl') || cy.state('window').origin
const runningEndToEndTests = baseUrl !== Cypress.config('proxyUrl')
if (runningEndToEndTests) {
// we can only request server-side code coverage
// if we are running end-to-end tests,
// otherwise where do we send the request?
const url = Cypress._.get(
Cypress.env('codeCoverage'),
'url',
'/__coverage__'
)
cy.request({
url,
log: false,
failOnStatusCode: false
})
.then(r => Cypress._.get(r, 'body.coverage', null), { log: false })
.then(coverage => {
if (!coverage) {
// we did not get code coverage - this is the
// original failed request
return
}
sendCoverage(coverage, 'backend')
})
}
...
```

# Workaround
> // node_modules/@cypress/code-coverage/support.js
```js
after(() => {
// there might be server-side code coverage information
// we should grab it once after all tests finish
const baseUrl = Cypress.config("baseUrl") || cy.state("window").origin;
const runningEndToEndTests = baseUrl !== Cypress.config("proxyUrl");
if (runningEndToEndTests) {
// we can only request server-side code coverage
// if we are running end-to-end tests,
// otherwise where do we send the request?
const url = Cypress._.get(Cypress.env("codeCoverage"), "url", "/__coverage__");
/* HERE IS THE FIX */
cy.exec(`curl ${url}`).then(r => {
if (!r || !r.stdout) {
// we did not get code coverage - this is the
// original failed request
return;
}
const coverage = JSON.parse(r.stdout).coverage;
sendCoverage(coverage, "backend");
});
/* END OF FIX */
}
....
```
I wasn't sure about the coding style that you have, that's why I'm opening an issue first and not a PR. Let me know if you want me to try something :)

By the way you are doing an amazing job at cypress ! 👏

# PS

Actually, before implementing the full stack code coverage on my big project, I've first made a minimal working repository with angular nestjs and cypress, to figure out how the implementation could be done.

Here is the link : https://github.com/flogh/cypress-angular-nestjs-code-coverage-fullstack

Maybe you'll want to add it to with the other implementation examples.