[build] Include MIT license in most NuGet packages (#8787)

Fixes: https://github.com/xamarin/xamarin-android/issues/8779

Updates all NuGet packages other than Microsoft.Android.Sdk to include
the MIT license at the root of the repo.

The license file name and contents have also been updated to improve
consistency with other dotnet repos.

LICENSE.TXT

@@ -1,8 +1,6 @@
-Xamarin.Android SDK
-
 The MIT License (MIT)
 
-Copyright (c) .NET Foundation Contributors
+Copyright (c) .NET Foundation and Contributors
 
 All rights reserved.
 
@@ -23,4 +21,3 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
-

build-tools/create-packs/Directory.Build.targets

@@ -47,7 +47,6 @@
   <Target Name="_SetGlobalProperties">
     <ItemGroup>
       <_GlobalProperties Include="-p:Configuration=$(Configuration)" />
-      <_GlobalProperties Include="-p:NuGetLicense=$(NuGetLicense)" />
       <_GlobalProperties Include="-p:IncludeSymbols=False" />
     </ItemGroup>
   </Target>
@@ -103,7 +102,7 @@
     />
     <!-- The .nupkg contains the files under /data/, so we need to move them -->
     <ItemGroup>
-      <_WLExtractedFiles Include="$(_SdkManifestsFolder)temp\LICENSE" />
+      <_WLExtractedFiles Include="$(_SdkManifestsFolder)temp\LICENSE.TXT" />
       <_WLExtractedFiles Include="$(_SdkManifestsFolder)temp\data\*" />
     </ItemGroup>
     <Move SourceFiles="@(_WLExtractedFiles)" DestinationFolder="$(_SdkManifestsFolder)microsoft.net.sdk.android" />

build-tools/create-packs/License.targets

@@ -1,12 +1,12 @@
-<!-- Ownership and LICENSE settings for .nupkg's -->
+<!-- Ownership and LICENSE.TXT settings for .nupkg's -->
 <Project>
   <PropertyGroup>
     <Authors>Microsoft</Authors>
     <Copyright>© Microsoft Corporation. All rights reserved.</Copyright>
     <PackageProjectUrl>https://github.com/xamarin/xamarin-android</PackageProjectUrl>
     <NuGetLicense Condition="Exists('$(XamarinAndroidSourcePath)external\monodroid\tools\scripts\License.txt')">$(XamarinAndroidSourcePath)external\monodroid\tools\scripts\License.txt</NuGetLicense>
-    <NuGetLicense Condition=" '$(NuGetLicense)' == '' ">$(XamarinAndroidSourcePath)LICENSE</NuGetLicense>
-    <PackageLicenseFile>LICENSE</PackageLicenseFile>
+    <NuGetLicense Condition=" '$(NuGetLicense)' == '' or '$(PackageId)' != 'Microsoft.Android.Sdk.$(HostOS)' ">$(XamarinAndroidSourcePath)LICENSE.TXT</NuGetLicense>
+    <PackageLicenseFile>LICENSE.TXT</PackageLicenseFile>
     <BeforePack>_GetLicense;$(BeforePack)</BeforePack>
   </PropertyGroup>
   <Target Name="_GetLicense">