Fix Resource Manager code to use native APIs before reflection

[PureWeen]

Description of Change

Fix Resource Manager to use native APIS to retrieve IDs before falling back to reflection. At some point the Resource.designer.cs class will most likely vanish so reflection will stop working (dotnet/android#5317). That's why this PR is targeting 4.8 so we can get this code in a little bit earlier than 5.0.

API Changes

Added:

• int ResourceManager.GetDrawableId(this Context context, string title)
• int ResourceManager.GetResource(this Context context, string title)

Platforms Affected

• Android

Testing Procedure

• UI Tests all pass
• Whatever additional testing you feel is missing from the UI Tests

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)

[jsuarezruiz]

The failing tests seems to be unrelated (CarouselViewPositionFromVisibilityChangeTest_google_pixel_2_8_1_0).

[PureWeen]

Test failures are unrelated