Add -ContentType Argument Completer for Invoke-RestMethod & Invoke-WebRequest cmdlets

[ArmaanMcleod]

PR Summary

Added ContentTypeArgumentCompleter for Invoke-RestMethod & Invoke-WebRequest cmdlets when using -ContentType parameter.

This completer uses reflection with .NET Media MIME types in System.Net.Mime.MediaTypeNames. Specifically just kept in the Application and Text media types, although we can add/remove these depending on ones which make sense.

I also used CompletionCompleters.GetMatchingResults so quotes are also handled.

Included tests to for the tab completion scenarios.

PR Context

Fixes #24917

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• User-facing changes
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  • Documentation needed
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    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode
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    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
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    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
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    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).
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[iSazonov]

I suggest to close the PR and wait WG conclusion in related issue. As tempting as this completer is, I doubt they'll approve.