feat(storage): add deleteSourceObjects option to Bucket::compose()

[salilg-eng]

This PR introduces the deleteSourceObjects option (boolean) to the Bucket::compose() method. When set to true, the library takes care of auto-deleting the source objects immediately and safely following a successful composition.

Transaction Safe: Cleanup is only triggered if composition succeeds. If composition fails and throws a ServiceException, the source files are safely preserved.
Polymorphic Handling: The deletion loop correctly handles lists containing both plain string paths (string[]) and typed StorageObject instances.
API Definition Consistency: deleteSourceObjects is added as a schema query parameter in the API Service Definition (storage-v1.json), ensuring consistent serialization down to the REST connection level.

[Hectorhammett]

If the option is a bool we should enforce the bool:

if (!$deleteSourceObjects instanceof bool) {
    throw new \InvalidArgumentException('The deleteSourceObjects option should be a boolean');
}

currently If the user passes a ['deleteSourceObjects'] = 52 the check for $deleteSourceObjects would be "true" even if the value is not a boolean.

It might behave as expected, but I strongly believe we should let the user know that a parameter is the wrong parameter.

[salilg-eng]

Thank you for the excellent feedback! Enforcing strict type checking for deleteSourceObjects is a great safety addition to prevent loose 'truthy' evaluations.

Regarding the implementation: in PHP, the instanceof operator is reserved only for checking objects against class/interface structures and does not support checking primitive types (like bool, string, int). Calling $val instanceof bool on a real boolean will look for a class named bool, return false, and therefore always throw the exception.

To resolve this, I've implemented the validation using PHP's built-in primitive validation function is_bool():

if (!is_bool($deleteSourceObjects)) {
    throw new \InvalidArgumentException('The deleteSourceObjects option should be a boolean.');
}

[Hectorhammett]

Oh yeah! My bad! haha it is in fact not instanceof bool but is_bool, you got it!