[Process] Add Process::disableOutput and Process::enableOutput methods
feature #10425 [Process] Add Process::disableOutput and Process::enableOutput methods (romainneutron)

This PR was merged into the 2.5-dev branch.

Discussion
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[Process] Add Process::disableOutput and Process::enableOutput methods

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #9007
| License       | MIT
| Doc PR        | https://github.com/symfony/symfony-docs/pull/3664

This is another implementation for #9007 that allows to disable the output/error-output storage in a Process in order to avoid using memory.
This is particularly useful when the process outputs large data and it's not read.

Commits
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a891e14 [Process] Add Process::disableOutput and Process::enableOutput methods