[11.x] Fix serve command with PHP_CLI_SERVER_WORKERS

[crynobone]

By default, serve command would restart child process when there's modification to the .env file. However, with PHP_CLI_SERVER_WORKERS set to larger than 1 the process doesn't close properly (port is still being used) and this cause the restart process to pick an incremented port number.

The changes here will unset PHP_CLI_SERVER_WORKERS value unless the command is executed with --no-reload option.

fixes #54574

[BrainStone]

Hey there. Apologies for necroing this PR/thread.

However I do have a few questions regarding the changes made here. If this isn't the appropriate place to ask, I'm happy to ask where ever you recommend me to.

Now I am wondering why it has been chosen to silently ignore a configuration value under fairly intransparent conditions (I mean the code is clear, but to people not knowing this code, the conditions are very unclear) instead of addressing the underlying issue at hand.
Is this an issue with the PHP development server? I've come across many comments and blurps that say something along the lines that the experimental support for PHP_CLI_SERVER_WORKERS in the built-in PHP development server either are or could be causing this issue where reloading doesn't free up the port, so the next instance gets a different port.

Additionally is there documentation for this behavior? I'm not saying there isn't any, just that I haven't come across any mention during my multi hour deep dive into why an update of Laravel suddenly caused timeouts in my dev server (which eventually lead me down the path of debugging why PHP_CLI_SERVER_WORKERS was getting ignored).