Refactor client tests, deprecate `addProtocolIfNotPresent`, fix abort bug, adjust documentation

[flevi29]

Pull Request

Related issue

Fixes #1922

What does this PR do?

• fixes bug where the wrong abort controller is passed to fetch
• adjusts documentation
• deprecates missing protocol in provided host
• refactors tests
  • removes some index tests, which are covered by #1918
  • moved some method tests to their own files (health, stats and some others)
  • removed bad host and permission tests #1945

Summary by CodeRabbit

• Refactor

  • Improved header management and timeout handling for HTTP requests.
  • Simplified and clarified internal documentation comments.
  • Enhanced URL protocol handling and removed deprecated utility functions.

• Bug Fixes

  • Improved error handling for task timeouts to prevent unexpected errors.

• Tests

  • Added new tests for health, stats, version, network, and core client functionality.
  • Removed outdated or redundant test suites to streamline testing.