…2130)
In `Xamarin.Android.Sdk.props` we have some inline C# code for a
MSBuild task named `SetVsMonoAndroidRegistryKey`.  Which is
understandable, since the code needed is so simple.  But thinking
about it, MSBuild has to *compile* this code to run it.  Which seems
inherently slower than if we compiled the code during our build.
Currently its entire parent target, `RedirectMonoAndroidSdkPaths`,
takes:
	157 ms  RedirectMonoAndroidSdkPaths                1 calls
I moved this task inside `Xamarin.Android.Build.Tasks.dll`, and we
appear to get some improvements "for free":
	 76 ms  RedirectMonoAndroidSdkPaths                1 calls
I looked at some past logs, and there are some times where the
`RedirectMonoAndroidSdkPaths` target was taking over 200ms.  I
suspect MSBuild might also have some caching functionality for
inlined C# code. There might be a cached assembly somewhere?
Not sure.
What makes this a better fix is that this target runs for all
builds--even builds with no changes.
General changes:
  - The `<UsingTask/>` doesn't need a condition, since it will be
    lazily evaluated anyways.
  - Used string interpolation where it looked nicer.
  - Used `LogDebugMessage()` and improved the log message.