Generate files for multiple versions

tl;dr:

replace

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

with

```php
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
<?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?)

This isn't even remotely tested, just a proof of concept to show what this kind of approach might look like

composer.json

@@ -7,20 +7,10 @@
             "lib/DateTime.php",
             "lib/DateTimeImmutable.php",
             "lib/Exceptions/",
-            "deprecated/Exceptions/",
             "generated/Exceptions/"
         ],
         "files": [
-            "deprecated/array.php",
-            "deprecated/datetime.php",
-            "deprecated/libevent.php",
-            "deprecated/misc.php",
-            "deprecated/password.php",
-            "deprecated/mssql.php",
-            "deprecated/stats.php",
-            "deprecated/strings.php",
             "lib/special_cases.php",
-            "deprecated/mysqli.php",
             "generated/apache.php",
             "generated/apcu.php",
             "generated/array.php",
@@ -42,6 +32,7 @@
             "generated/ftp.php",
             "generated/funchand.php",
             "generated/gettext.php",
+            "generated/gmp.php",
             "generated/gnupg.php",
             "generated/hash.php",
             "generated/ibase.php",
@@ -59,6 +50,7 @@
             "generated/mbstring.php",
             "generated/misc.php",
             "generated/mysql.php",
+            "generated/mysqli.php",
             "generated/network.php",
             "generated/oci8.php",
             "generated/opcache.php",
@@ -111,7 +103,7 @@
         "php-parallel-lint/php-parallel-lint": "^1.4"
     },
     "scripts": {
-        "lint": "parallel-lint deprecated/ lib/ tests/",
+        "lint": "parallel-lint lib/ tests/",
         "test": "phpunit",
         "phpstan": "phpstan analyse",
         "cs-fix": "phpcbf",