Adds a --silent option to the CLI

[gottfrois]

Description

This PR adds a -s, --silent option which deactivate Puma messages displayed on the prompt.

Without the option:

$ bundle exec bin/puma test/rackup/hello.ru
Puma starting in single mode...
* Puma version: 5.5.2 (ruby 2.6.6-p146) ("Zawgyi")
*  Min threads: 0
*  Max threads: 5
*  Environment: development
*          PID: 88245
* Listening on http://0.0.0.0:9292
Use Ctrl-C to stop
^C- Gracefully stopping, waiting for requests to finish
=== puma shutdown: 2022-01-18 16:38:07 +0100 ===
- Goodbye!

With the option:

$ bundle exec bin/puma --silent test/rackup/hello.ru
^C%

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• I have added (or updated) appropriate tests if this PR fixes a bug or adds a feature.
• My pull request is 100 lines added/removed or less so that it can be easily reviewed.
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• All new and existing tests passed, including Rubocop.

[MSP-Greg]

Do we really want to silence STDERR?

[gottfrois]

Good catch, might want to leave the stderr as it is

[MSP-Greg]

Using @events = Events.new NullIO.new, STDERR seems to work, as errors are written.

I think the test will always pass, as Puma::Events.null.class or any call to Puma::Events.new will have a class of Puma::Events.

Not sure about this, let's see what others think...

[nateberkopec]

Agree with Greg. Also, isn't this option usually called quiet?

[dentarg]

Puma has -q, --quiet, but it is used to silent the request logging (and it is on by default), from puma --help,

-q, --quiet                      Do not log requests internally (default true)

(we have -v, --log-requests to turn it on)

[gottfrois]

I've reverted the stderr not to be silent as suggested.

[nateberkopec]

Change looks super clean. Glad this wasn't too hard to implement.