(app) Resolve a bug where the state changes isn't detected properly

[tchaton]

What does this PR do?

The DeepDiff generates an unprocessed key for Path, Drive objects and therefore leads to wrong detection of state update. This PR converts Drive, Path objects to dict for DeepDiff to make a comparaison.

The test breaks on master.

___________________________________ test_lightning_app_has_updated ____________________________________

    def test_lightning_app_has_updated():
        app = TestLightningHasUpdatedApp(FlowPath())
>       MultiProcessRuntime(app, start_server=False).dispatch()

tests/tests_app/core/test_lightning_app.py:997: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
src/lightning_app/runners/multiprocess.py:103: in dispatch
    self.app._run()
src/lightning_app/core/app.py:427: in _run
    done = self.run_once()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <tests_app.core.test_lightning_app.TestLightningHasUpdatedApp object at 0x13ceae250>

    def run_once(self):
        res = super().run_once()
        if self.root.w.path is not None:
            self.counter += 1
    
        if self.counter == 2:
>           assert not self._has_updated
E           assert not True
E            +  where True = <tests_app.core.test_lightning_app.TestLightningHasUpdatedApp object at 0x13ceae250>._has_updated

tests/tests_app/core/test_lightning_app.py:990: AssertionError

Fixes #<issue_number>

Does your PR introduce any breaking changes? If yes, please list them.

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you list all the breaking changes introduced by this pull request?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or minor internal changes/refactors)

PR review

Anyone in the community is welcome to review the PR.
Before you start reviewing, make sure you have read the review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

Did you have fun?

Make sure you had fun coding 🙃

cc @Borda