refactor!: simplify namespaces to make public API more pythonic

[federicobond]

For reviewing, it's best to follow the changes commit by commit.

This reduces the number of public namespaces in the sdk, following what we agreed on #101

I consolidated some modules into a single file when it made sense. The alternative would have been to prefix the internal namespace files with underscores and re-export the relevant symbols from __init__.py but it added a lot of boilerplate with little benefit. If the modules grow in size to make this necessary, it can be done later without breaking compatibility with existing users.

[codecov]

Codecov Report

Merging #172 (7444b29) into main (6f7cdb8) will decrease coverage by 0.54%.
The diff coverage is 95.31%.

@@            Coverage Diff             @@
##             main     #172      +/-   ##
==========================================
- Coverage   93.47%   92.93%   -0.54%     
==========================================
  Files          23       16       -7     
  Lines         460      439      -21     
==========================================
- Hits          430      408      -22     
- Misses         30       31       +1     

Flag	Coverage Δ
unittests	92.93% <95.31%> (-0.54%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
open_feature/evaluation_context.py	90.90% <ø> (ø)
open_feature/hook/hook_support.py	86.48% <86.48%> (ø)
open_feature/flag_evaluation.py	97.72% <97.67%> (ø)
open_feature/api.py	100.00% <100.00%> (ø)
open_feature/client.py	95.60% <100.00%> (ø)
open_feature/exception.py	84.37% <100.00%> (ø)
open_feature/hook/__init__.py	86.11% <100.00%> (ø)
open_feature/provider/in_memory_provider.py	98.11% <100.00%> (-0.04%)	⬇️
open_feature/provider/no_op_provider.py	100.00% <100.00%> (ø)
open_feature/provider/provider.py	75.00% <100.00%> (ø)
... and 2 more

... and 1 file with indirect coverage changes

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[beeme1mr]

This looks great, thank you! Please make sure to update the examples on the readme.

[toddbaert]

I'll review this first thing next week. Thanks @federicobond

[toddbaert]

If the modules grow in size to make this necessary, it can be done later without breaking compatibility with existing users.

👍

[toddbaert]

LGTM!

[toddbaert]

Obviously this is a breaking change, but I have no issue merging it. I'll do so in the next few days unless I hear objections from the other (more Python-literate) reviewers.