[php-src] Issue #22404: Test for bug 62900 can make use of TEST_PHP vars

Issue: https://github.com/php/php-src/issues/22404
Author: orlitzky

### Description

We're going to wind up skipping this anyway using `SKIP_IO_CAPTURE_TESTS=1`, but in case it affects someone else... in `ext/soap/tests/bugs/bug62900.phpt`, we go to a lot of trouble to ensure that the development PHP (and its settings) are used:

```php
$args = ["-d", "display_startup_errors=0", "-d", "extension_dir=" . ini_get("extension_dir"), "-d", "extension=" . (substr(PHP_OS, 0, 3) == "WIN" ? "php_" : "") . "soap." . PHP_SHLIB_SUFFIX];
if (php_ini_loaded_file()) {
    // Necessary such that it works from a development directory in which case extension_dir might not be the real extension dir
    $args[] = "-c";
    $args[] = php_ini_loaded_file();
}

...

$proc = proc_open([PHP_BINARY, ...$args, __DIR__.'/bug62900_run'], [1 => ["pipe", "w"], 2 => ["pipe", "w"]], $pipes);
```

Rather than calling `PHP_BINARY` and hacking the args, I think what we want here is to invoke `TEST_PHP_EXECUTABLE`?

### PHP Version

```plain
git master
```

### Operating System

Gentoo linux