ref: Remove currentHub from SentrySDK

[philipphofmann]

📜 Description

Remove SentrySDK.currentHub and SentrySDK.setCurrentHub, which are only
needed internally and by hybrid SDKs. They are not intended to be public API.

This breaks Hybrid SDKs, but we are going to fix this with adding captureEnvelope and storeEnvelope to SentrySDK.m but not in the header. The hybrid SDKs can create a category to make these two methods accessible. We use this pattern for the test initializers already.

💡 Motivation and Context

See getsentry/develop#248 (comment)

💚 How did you test it?

CI.

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the CHANGELOG if needed
• I updated the docs if needed
• Review from the native team if needed
• No breaking changes

🔮 Next steps

[marandaneto]

@philipphofmann what would be the alternative for SentrySDK.currentHub().capture(envelope: envelope) ? before removing, we need to guarantee that this is possible either via SentrySDK static class or elsewhere as Hybrid SDKs rely on it

[philipphofmann]

@philipphofmann what would be the alternative for SentrySDK.currentHub().capture(envelope: envelope) ? before removing, we need to guarantee that this is possible either via SentrySDK static class or elsewhere as Hybrid SDKs rely on it

Sorry, I should have put this in the PRs description. This is the first step of this comment here: getsentry/develop#248 (comment). See point 2.

[marandaneto]

NICE, LGTM