value of 'wp-parser-namespace_children' option incorrect after parsing source with hierarchical nmespaces

When parsing code that contains hierarchical namespaces, e.g.,

namespace My\Hierarchical\Namespace;

class MyClass {
...
}

terms are created for each step in the hierarchy (My, Hierarchical and Namespace in the example above), but since cache invalidation is suspended during a parse, the wp-parser-namespace_children option is never updated.

This results in, among other things, only the top-level namespace term showing in the WP_Terms_List_Table in the backend

WP_Parser\Importer::import() correctly deletes wp-parser-package_children and wp-parser-since_children at the end of the parse (which will result in them being rebuilt at the appropriate time), but it seems that wp-parser-namespace_children was forgotten.

PR coming shortly.

Start in WP_Parser\Importer::import(), where the parser already removes the wp-parser-package_children and wp-parser-since_children options after parsing. Confirm that hierarchical namespace terms leave wp-parser-namespace_children stale, then ensure it is invalidated at the same point. Verify that all namespace levels appear in the WP_Terms_List_Table after parsing.