test(docs-infra): improve debugging when docs example tests fail without exiting (#43683)
test(docs-infra): improve debugging when docs example tests fail without exiting (#43683)

When the docs examples tests run with `--cliSpecsConcurrency` greater
than 1 (as happens on CI), the output of each process is [buffered][1]
(to avoid interleaved output from multiple, parallel processes) and is
only printed out once the process exits (either successfully or with an
error). However, in cases where a process did not exit, the buffered
output would be never printed out, thus making debugging the failure
harder. This is the case, for example, if a build error happens during
`ng e2e`. This can be seen in action in [this CI job][2], where the job
fails due to no output, but the error (which is an incompatible TS
version) is never printed out.

To make debugging such situations easier in the future, this commit
updates the `spawnExt()` helper to reject (causing the buffered output
to be printed out) if there is no output from the spawned process for
more than 5 minutes.

[1]: https://github.com/angular/angular/blob/c721135e370b34c840756bcfb22c8119b4c8c452/aio/tools/examples/run-example-e2e.mjs#L293
[2]: https://circleci.com/gh/angular/angular/1061751

PR Close #43683

angular/angular,shairez/angular,ocombe/angular,gnomeontherun/angular,manekinekko/angular,gkalpak/angular,JiaLiPassion/angular,angular-indonesia/angular,brandonroberts/angular,angular/angular,ocombe/angular,manekinekko/angular,ocombe/angular,manekinekko/angular,brandonroberts/angular,manekinekko/angular,JiaLiPassion/angular,ocombe/angular,manekinekko/angular,brandonroberts/angular,ocombe/angular,JiaLiPassion/angular,angular-indonesia/angular,angular-indonesia/angular,gkalpak/angular,gnomeontherun/angular,brandonroberts/angular,brandonroberts/angular,shairez/angular,shairez/angular,shairez/angular,gnomeontherun/angular,angular-indonesia/angular,gkalpak/angular,gnomeontherun/angular,angular/angular,ocombe/angular,brandonroberts/angular,manekinekko/angular,gkalpak/angular,shairez/angular,JiaLiPassion/angular,angular/angular