feat: update provider status when provider emits events

[federicobond]

I also made openfeature.provider.registry a private module and moved the registry singleton inside it.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.15385% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 97.58%. Comparing base (faf02a9) to head (9aa8a75).

Files	Patch %	Lines
openfeature/provider/_registry.py	88.88%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #309 +/- ## ========================================== + Coverage 97.10% 97.58% +0.47% ========================================== Files 27 27 Lines 1176 1202 +26 ========================================== + Hits 1142 1173 +31 + Misses 34 29 -5 ``` | [Flag](https://app.codecov.io/gh/open-feature/python-sdk/pull/309/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-feature) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/open-feature/python-sdk/pull/309/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-feature) | `97.58% <96.15%> (+0.47%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-feature#carryforward-flags-in-the-pull-request-comment) to find out more.

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[federicobond]

@gruebel found a couple of bugs with the event logic around provider initialization/shutdown, all new changes are in the latest commit.

[gruebel]

@federicobond new changes look good 🙂