Add environment variable to so `persistent_timeout` option of puma can be changed.

This is how it looks in the example in the Puma README

* Code quality pass

* Typofix

* Update applications_controller_spec.rb

* Update applications_controller_spec.rb

* Revert "Default puma to running on localhost only. (#8429)"

This reverts commit 2a59c6a5e7.

Setting port after binding a unix socket puma listen to both of an unix
socket and TCP/IP, which is not a desired behavior.

* Allow puma to listen Unix socket

* streaming: Show the whole listening address instead of the port

Port is not always appropriate (e.g. Unix socket)

* streaming: Close server before exiting

This change especially allows to remove Unix socket before exiting.