Generate files for multiple versions

[shish]

tl;dr:

replace

$function_list = read_docs();
generate_files($function_list, "../generated/");

with

foreach(["8.1", "8.2", "8.3", "8.4"] as $version) {
    exec("cd docs && git checkout $version");
    $function_list = read_docs();
    generate_files($function_list, "../generated/$version/");
}

generate a bunch of stubs like generated/misc.php:

<?php
if(PHP_VERSION == "8.1") require_once __DIR__ . "/8.1/misc.php";
if(PHP_VERSION == "8.2") require_once __DIR__ . "/8.2/misc.php";
if(PHP_VERSION == "8.3") require_once __DIR__ . "/8.3/misc.php";
if(PHP_VERSION == "8.4") require_once __DIR__ . "/8.4/misc.php";

This also automates generation of "deprecated" safe functions (ie, instead of hard-coding deprecated/apache.php, any functions which needed safe wrappers in 8.1 but no longer need safe wrappers in 8.2 will have no-op stubs generated instead)

Currently the Exceptions are shared between all versions, which I think is a good idea? (Thoughts, anybody?)

[jhdxr]

The CI looks unhappy because of redeclaration, probaly caused by files pending for clean up?

I think we may split this huge PR into several small PR (one for generating scripts, and one for each PHP version), which makes the PR easy to read & review.

[shish]

I am unsure why the generator script is giving different outputs on my laptop and in CI testing D:

[silasjoisten]

Jesus 😅 just seen the lines added and was a bit afraid

[silasjoisten]

I will check rector stuff tomorrow

[shish]

No, I don't see any way of meaningfully splitting it into smaller commits without breaking it

Update - I've split the "removal of manually-managed deprecated functions" into a separate commit (Which can be reviewed in isolation as #536), which is removing an important feature, but isn't technically breaking it (and the following commit adds automatically-managed deprecated functions, so once both commits land, we will be good)

[shish]

Given the lack of any positive or negative feedback, I'm going to YOLO this into the master branch and try to get an alpha release out sooner rather than later - if suddenly people start complaining, we can fix forwards