Add environment variable to configure the server shutdown timeout

[rijkvanzanten]

The timeout ms of terminus is hardcoded to 1000 in the server shutdown. We should add a new SERVER_SHUTDOWN_TIMEOUT environment variable to configure this.

Discussed in #17237

^{Originally posted by onordgren January 19, 2023}
Hello! We're running directus in k8s and would like to be able to control the timeout period in the terminus handler. From the source code it looks like it's hard coded at 1000ms. Is there some other recommended way of doing this, was thinking of maybe doing it in the server.stop hook. Or would you consider adding a configuration option to be able to set the terminus timeout?

[github-actions]

Linear: ENG-521