Use auto_globals_jit to make classic mode like worker mode for some use-cases

Describe your feature request

Is your feature request related to a problem? Please describe.

We (myself and @SpencerMalone) were discussing how to use workers to 'bootstrap' an application, then wait for a request, then die() to allow for classical applications to get some performance without having to rewrite them for worker mode.

Describe the solution you'd like

We could maybe specify in the caddyfile:

preheat public/index.php

for a route, then we spawn up some workers that start up the file and once a superglobal is accessed, we pause execution until a request comes through, fill in the superglobals, then continue the script. This requires the use of auto_globals_jit to make work, but older/custom applications will be able to take advantage of performance from frankenphp while implementing worker scripts.