Add internal testing tools package

[louiszawadzki]

What does this PR do?

This adds a new package for internal UI-level testing.
The package has 3 methods:

• enable (to be called before initializing the SDK): registers hooks to capture events
• getAllEvents: returns all captured events for a given feature
• clearData: removes all captured events

Motivation

Enable UI-level testing for the SDK.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• If this PR is auto-generated, please make sure also to manually update the code related to the change

[maxep]

It looks great on the iOS side, well done!
I have left a coupe of suggestions.

[0xnm]

nice work! I added few comments/thoughts.

[0xnm]

If we don't want to make it available to the customers, we need to make this class internal.

Suggested change

	object DatadogSDKWrapperStorage {
	internal object DatadogSDKWrapperStorage {

[louiszawadzki]

If I make it internal, I cannot import it in the internal testing module.
Is it possible to still import it?

And I think it can be ok to leave it available to customers. Most of them won't do anything, and maybe that can make things a little easier for some customers with hybrid applications.

[0xnm]

Let's keep it public then, but if it used only for the tests, nothing in the name reflects that the intended usage is for the tests only.

[louiszawadzki]

It will also be used in Session Replay to make sure we use the same core for all features - it's one of the next tasks on the topic.
When we'll split the RN SDK in core/RUM/Logs/Trace this will also be used to get the core in the feature packages.

Let me know if you think we should still change the name to something more explicit here.

[0xnm]

So this call will do another setSdkCore call, but with StubSDKCore this time? It is a bit non-intuitive by looking on the class name. Maybe we need some method there which has something related to the stubbing directly in the name?

[louiszawadzki]

We do not do another setSdkCore call directly, but we notify all listeners, and one of them happens to be setting the SdkCore.
I don't think this is a good idea to reflect in the name of notifyOnInitializedListeners that it's currently only being used for internal testing since it is in the main SDK package and we might as well add other callbacks in the future.

I can add a comment in the test and above the function to make it clearer, would that work for you?