Feature/datadog crash logging

[ninovanhooff]

Why is this important?

For the techops for apps workgroup we are exploring Datadog. This PR is not meant do be merged, just as a poc.
We probably will be using Kermit + Crashlytics as default.

• create an interface for logging so that unit tests don't have to depend on Datadog (which is a problem for iOS)
• replace Kermit logging by Datadog
• replace Crashlytics by Datadog
• remove firebase since it is not used anymore

Notes

• Needs the client and app secrets. client token here: https://app.datadoghq.eu/organization-settings/client-tokens
  application Id: not sure how to find it in datadogs interface 😵 . It is 01af331e-658f-45df-be2d-e1d16b53d26e
  edit: you can find the needed credentials in step 4 of the setup steps for this app: "Initialize RUM"
• ios tests in the shared source set are not run automatically anymore, because shared has a dependency on datadog and that is a problem for a reason I don't fully understand. These tests can be run from xcode, I think. Perhaps this github action could cover this loss: https://github.com/marketplace/actions/swift-test-action-for-datadog

Considerations in case we want to merge this to main sometime

• maybe only merge the part where logging is hidden behind an interface, so datadog does not become the default but it is more easily added
• where to put the secrets? currently in the repo (shared/build.gradle.kts)
• For what branches to run the workflows and dsym upload steps