chore: replace query-string with simple implementation

[KuSh]

The implementation could have been further simplified by using URLSearchParams, but tests require that separators in array-type parameters not be encoded to not be encoded.

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• [ ] Make sure to open a GitHub issue as a bug/feature request before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• [x] Ensure the tests and linter pass
• [x] Code coverage does not decrease (if any source code was changed)
• [ ] Appropriate docs were updated (if necessary)