refactor: DP system simplifications

[Youssef1313]

GitHub Issue (If applicable): closes #

PR Type

What kind of change does this PR introduce?

What is the current behavior?

OverrideMetadata is a WPF thingy and not present in WinUI. We shouldn't need it. It's currently used only to override default values, which WinUI does in a different way.

For Button, [Horizontal|Vertical]ContentAlignmentProperty is already Center unless UseLegacyContentAlignment is set to true (no one should be using this legacy flag actually)

For ProgressBar, Maximum correct value is actually 1

For ScrollViewer, [Horizontal|Vertical]ContentAlignmentProperty is actually Center in WinUI so our override is wrong

What is the new behavior?

PR Checklist

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• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
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• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
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Other information

Internal Issue (If applicable):

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