Use kwargs for long lists of EngineCoreRequest arguments in tests and fix extra kwargs

[qthequartermasterman]

Purpose

In most places in the tests, instantiations of EngineCoreRequest use kwargs instead of positional arguments. There are too many arguments to keep track of positionally. Additionally after recent refactors simplifying the arguments passed in for multimodal(see #23779), one instance was not correspondingly updated. The tests were still passing as a happy accident despite values were getting passed into wrong arguments.

This change originally came up in #24278 (comment), by @DarkLight1337, but because we later refactored that PR to not require having to modify those instantiations at all, I broke this out into its own PR for easier review.

Test Plan

No new tests are needed.

Test Result

All of the tests in tests/detokenizer/test_min_tokens.py and tests/tokenization/test_detoknize.py are passing in my local environment. Pending CI, this PR should be good to go.

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
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[gemini-code-assist]

Code Review

This pull request refactors the instantiation of EngineCoreRequest in test files to use keyword arguments, which significantly improves code readability and maintainability. This change also correctly fixes a bug where positional arguments were being passed in the wrong order. The updated code is much clearer and less prone to errors. The changes look good and I have no further suggestions.