ScrollHeader and Behaviors tweak

[hermitdave]

Issue: #1659

PR Type

What kind of change does this PR introduce?
ScrollHeader and Behaviors tweak

[] Bugfix
[ ] Feature
[ ] Code style update (formatting)
[x] Refactoring (no functional changes, no api changes)
[ ] Build or CI related changes
[ ] Documentation content changes
[x] Sample app changes
[ ] Other... Please describe:

What is the current behavior?

ScrollHeader requires TargetListView to be set. It should not be mandatory as ScrollHeader is set to ListView / GridView header.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Docs have been added / updated (for bug fixes / features)
• Sample in sample app has been added / updated (for bug fixes / features)
• Tests for the changes have been added (for bug fixes / features) (if applicable)

What is the new behavior?

Make TargetListViewBase in ScrollHeader optional
Mark TargetListViewBase as obsolete
Tweak FadeHeaderBehavior, QuickReturnHeaderBehavior and StickyHeaderBehavior

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[hermitdave]

@pdehne any thoughts on this?

[pdehne]

Looks good! Getting rid of the TargetListViewBase property makes it definetely easier to use.

[windowstoolkitbot]

This PR is linked to unclosed issues. Please check if one of these issues should be closed: #1659