[workload] rename Microsoft.Maui.Controls.Sdk

[jonathanpeppers]

Description of Change

It is a bit confusing the top level Sdk pack for the Maui workload is
named Microsoft.Maui.Controls.Sdk. This pack is imported even when
you're not using "Controls", such as $(UseMauiCore),
$(UseMauiAssets), etc.

Let's rename:

• Microsoft.Maui.Controls.Sdk -> Microsoft.Maui.Sdk
• Microsoft.Maui.Controls.Sdk.targets -> Microsoft.Maui.Sdk.targets
• Microsoft.Maui.Controls.Sdk.After.targets -> Microsoft.Maui.Sdk.After.targets

This change should hopefully be transparent to everyone, and no one
will notice?

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)
• Targets a single property for a single control (or intertwined few properties)
• Adds the property to the appropriate interface
• Avoids any changes not essential to the handler property
• Adds the mapping to the PropertyMapper in the handler
• Adds the mapping method to the Android, iOS, and Standard aspects of the handler
• Implements the actual property updates (usually in extension methods in the Platform section of Core)
• Tags ported renderer methods with [PortHandler]
• Adds an example of the property to the sample project (MainPage)
• Adds the property to the stub class
• Implements basic property tests in DeviceTests

Does this PR touch anything that might affect accessibility?

No

[jonathanpeppers]

@pjcollins to just double-check this won't break VS insertions to rename a pack.

[mattleibow]

Looks like all the spots were changed.

Nice to get accurate names!

[pjcollins]

I don't believe this will cause any issues wrt VS insertion.