The argument names are defined here:

https://github.com/php/php-src/blob/PHP-8.0.0/ext/standard/basic_functions_arginfo.h#L1773-L1780

Since before 8.0 the named arguments were not part of the interface, we
don't care about the intermediate steps of the proc_open definition. For
consistency, this makes the definition the same across all versions.

This also fixes the type for the `options` argument already in
CallMap_historical to be nullable.

The names of the arguments are now consistent across versions, while the
delta for 7.4 reflects the change of the `command` argument from
`string` to `string|array`.