Change MenuItem to inherit from HeaderedItemsControl

[skendrot]

PR Type

What kind of change does this PR introduce?
Change MenuItem to inherit from HeaderedItemsControl instead of ItemsControl. Remove the Header and HeaderTemplate properties from MenuItem

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

What is the current behavior?

MenuItem inherits from ItemsControl and has a local Header and HeaderTemplate property

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?

MenuItem now inherits from HeaderedItemsControl and takes advantage of it's Header and HeaderTemplate properties

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[skendrot]

I did not change the docs for this because it notes a special behavior when using the Header property.