ref(flags): underscore featureflags module and identifier

[aliu39]

Follow-up to #3860, which hasn't been released yet

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
13784	1	13783	4153

View the top 1 failed tests by shortest run time

tests.test_transport test_transport_works[threads-False-gzip-0-True-flush-False]

Stack Traces | 2.52s run time

tests/test_transport.py:187: in test_transport_works
    assert capturing_server.captured
E   AssertionError: assert []
E    +  where [] = <CapturingServer(<class 'tests.test_transport.CapturingServer'>, started 139966323615488)>.captured

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[antonpirker]

This is a breaking change and needs a major update for the SDK.

Is this something we MUST have or it is just a nice too have?
I would not want to make this breaking change only for cosmetic reasons.

[antonpirker]

@aliu39 and @cmanallen the FeatureFlagsIntegration is not documented yet so I guess it is still in beta or some kind of stealth mode, right?
If it is not yet used by a lot of users, we probably can rename it without a major update.

[antonpirker]

In our feature flag documentation we state that feature flag tracking is a beta feature.

Also FeatureFlagsIntegration is not yet documented at all.

So renaming this is OK in a minor release.

[cmanallen]

@antonpirker The featureflags modules hasn't been released yet so unless someone is running from master no one has ever used the integration. That's why we felt it was safe. Thanks for merging this! :)