Enable UsePkce by default for Google and Facebook auth

[FranklinWhale]

Enable UsePkce by default for Google and Facebook auth

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Summary of the changes (Less than 80 chars)

Description

1. Set UsePkce to true in GoogleOptions and FacebookOptions
2. BuildChallengeUrl in GoogleHandler now calls base.BuildChallengeUrl
3. Rename AddQueryString to SetQueryParam in GoogleHandler
4. Refactor ChallengeWillTriggerRedirection in GoogleTests to check query dictionary instead of string matching

Contributes to #4684

[ghost]

Thanks for your PR, @FranklinWhale. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[FranklinWhale]

@Tratcher Unfortunately, with the new BuildChallengeUrlQuery method, the build cannot be successful. If having a new method is not preferred, it is possible to call QueryHelpers.ParseQuery(base.BuildChallengeUrl(properties, redirectUri)) in GoogleHandler then modify the Dictionary. What do you think?

[Tratcher]

Changing a public/protected API signature is not allowed under our breaking changes guidelines. Try the other approach.

[Tratcher]

Please check on the test failure.
https://dev.azure.com/dnceng-public/public/_build/results?buildId=92270&view=ms.vss-test-web.build-test-results-tab&runId=1943220&resultId=109738&paneView=debug

[FranklinWhale]

Added comment and fixed the test.

[Tratcher]

Thanks