Add timeout parameter to Go To Url keyword and improve tests

[Dor-bl]

This pull request enhances the go_to_url keyword in the AppiumLibrary to support an optional page load timeout parameter and adds comprehensive tests for this new functionality. The main changes include updating the implementation to handle the timeout logic, improving documentation, and ensuring robust test coverage for various scenarios.

Will resolve: #440

Enhancements to go_to_url:

• The go_to_url method in _applicationmanagement.py now accepts an optional timeout argument, allowing users to specify a maximum page load time using either seconds or time strings. The method temporarily sets the page load timeout, restores the original timeout after navigation, and handles both normal and exceptional cases.
• The docstring and usage examples for go_to_url have been updated to reflect the new timeout parameter and its supported formats.

Test coverage improvements:

• Multiple new unit tests have been added in test_applicationmanagement.py to verify:
  • Default behavior when no timeout is given.
  • Correct handling of numeric and string timeouts.
  • Proper restoration of the original timeout after navigation, including when navigation fails.