The declaring op_array is used for multiple purposes:
 * Generating a PFA name
 * Finding the filename
 * Finding whether op_array is cached, and therefore whether the PFA should be
   cached too

However it's not available when evaluating a PFA AST.

Remove the declaring_op_array argument, and pass the relevant information
directly:
 * Generate the PFA name at compile time, pass it as argument to zend_partial_create()
 * Pass the filename and a cacheable flag as argument to zend_partial_create()

Pre-bound arguments are bound to the generated closure's lexical vars:

```
function f($a, $b) {}
$f = f(1, ?);

// Generates:
$tmp = 1;
$f = function ($b) use ($tmp) {
    return f($tmp, $b);
};
```

Detect which pre-bound arguments are constant and burn them into the generated
closure instead:

```
function f($a, $b) {}
$f = f(1, ?);

// Generates:
$f = function ($b) {
    return f(1, $b);
};
```