fix: Improve SelectedNetworkController tests with more robust behavio…

[VolodymyrBg]

…ral testing

Explanation

This commit enhances the test coverage for SelectedNetworkController by implementing more comprehensive behavioral tests that better simulate real-world interactions:

1. Added tests for snap domains that verify they consistently use the globally selected network when network changes occur
2. Improved metamask domain tests to ensure it always follows the globally selected network through network changes
3. Added robust behavioral testing for preference changes that show how domain requests are properly routed based on useRequestQueue settings
4. Implemented multi-domain tests to verify correct behavior when toggling between different network preferences

These changes replace the simplistic mocking approaches with more realistic testing scenarios that better verify the controller's behavior in production environments.

References

TODO

Changelog

@metamask/package-a

• : Your change here
• : Your change here

@metamask/package-b

• : Your change here
• : Your change here

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes