Extensions can extends the core test ExtensionJsonTestBase which provides some more validation for keys in extension.json.
In the special case for HookHandlers keys, the test fails when a optional extension, which hooks are implemented, is not installed, because it fails on loading the hook interfaces.
For optional extension there exists own hook handlers as the class is also not loaded in production code, when it would be in own class with core hooks.
As more extensions gets converted to use HookHandlers (T263353) some "native" support in this test would be very useful.
Maybe for the begin just a mapping from the key in HookHandlers to the extension name to filter out, that could replace some overwrites.
Or the HookHandlers in extension.json gets a required key or similiar option.
Overwrites: