[Fix Configuration Loader] Migrate Thread Scheduling Logic into BraintreeClient

[sshropshire]

Note: This PR is Part 5 in a series of refactoring PRs to eliminate ConfigurationLoader race conditions. Previous PR: #1133 [Fix Configuration Loader] Prevent Race Condition

Summary of changes

• This PR migrates multi-threading logic into BraintreeClient to set up an eventual easy migration to coroutines
• In the future, we can leverage co-routines to reduce the SDK's responsibility to create background threads.
• Upcoming Tasks to finish Fix Configuration Loader PR series:
  • Remove HttpClient and make all networking clients thread synchronous by default
  • Implement retry logic in ConfigurationLoader

Checklist

• [ ] ~Added a changelog entry~
• [x] Relevant test coverage

Authors

List GitHub usernames for everyone who contributed to this pull request.

• @sshropshire

[jaxdesmarais]

@tdchow is this PR and the PRs in the base branch something we still need to get into v5? It's been inactive for a bit so wasn't sure if this still needed another 👍 and for us to open a PR from base to main.

[tdchow]

@tdchow is this PR and the PRs in the base branch something we still need to get into v5? It's been inactive for a bit so wasn't sure if this still needed another 👍 and for us to open a PR from base to main.

@sshropshire is this part 5 the final changes needed for the configuration loader refactor? would we be good merging the feature branch into main after this PR?

[sshropshire]

It's definitely close. There's retry logic that needs to be re-implemented for this to be fully complete. It used to happen in HttpClient but it makes more sense for it to live in ConfigurationLoader.

[saperi22]

@sshropshire @tdchow what state is this PR in? Does it need more work or are we good to merge?

[tdchow]

@saperi22 - We decided to put the ConfigurationLoader work on hold for now. I'll go ahead and close this PR.