refactor: move evaluation classes into AmplitudeAnalytics module

[FabricioFFC]

Summary

We're migrating to the Amplitude SDK, and during this process, we noticed that some module names (e.g., Evaluation) conflict with the third party feature-flag SDK we currently use.

This PR resolves the conflict by adding all classes and modules that were not already namespaced to the AmplitudeExperiment module.

Besides that there are some minor changes included:

• CycleError was duplicated, so it was removed
• The link to the CONTRIBUTING is now updated with the correct link
• update concurrent-ruby to support newer versions

For reviewers: enabling Hide whitespace will reduce noise in the diff and make the PR easier to review. :)

Checklist

• Does your PR title have the correct title format?
• Does your PR have a breaking change?: No

[kyeh-amp]

@FabricioFFC thank you so much for bringing this up! I've used your branch to start and made some slight adjustments on your take here: #77

I hope you don't mind - I felt this would be faster than the back-and-forth.

[FabricioFFC]

@FabricioFFC thank you so much for bringing this up! I've used your branch to start and made some slight adjustments on your take here: #77

I hope you don't mind - I felt this would be faster than the back-and-forth.

@kyeh-amp no problem. Are you planning to include the other small changes that aren't related to the AmplitudeExperiment module as well, or should those go into a follow-up PR?

[kyeh-amp]

This change was included in today's release of v1.7.1. Closing this now.