Describe the bug

A clear and concise description of what the bug is.

• Is this bug a regression in the toolkit? If so, what toolkit version did you last see it work:

Steps to Reproduce

• Can this be reproduced in the Sample App? (Either in a sample as-is or with new XAML pasted in the editor.) If so, please provide custom XAML or steps to reproduce. If not, let us know why it can't be reproduced (e.g. more complex setup, environment, dependencies, etc...)

Steps to reproduce the behavior:
Create a GridSplitter in a context with a RightToLeft FlowDirection
Adjust the GridSplitter.
Observe the GridSpillter move opposite the curser

Expected behavior

Even when in RightToLeft, the GridSplitter should follow the curser

Screenshots

If applicable, add screenshots to help explain your problem.

Environment

NuGet Package(s):
Microsoft.Toolkit.UWP.UI.Controls

Package Version(s):
7 preview 4

Windows 10 Build Number:

• Fall Creators Update (16299)
• April 2018 Update (17134)
• October 2018 Update (17763)
• May 2019 Update (18362)
• May 2020 Update (19041)
• Insider Build (build number: )

App min and target version:

• Fall Creators Update (16299)
• April 2018 Update (17134)
• October 2018 Update (17763)
• May 2019 Update (18362)
• May 2020 Update (19041)
• Insider Build (xxxxx)

Device form factor:

• Desktop
• Xbox
• Surface Hub
• IoT

Visual Studio

• 2017 (version: )
• 2019 (version: 16.8.3)
• 2019 Preview (version: )

## Additional context
Add any other context about the problem here.