chore(nuget): Add support for macosx (#553)

Additionally
- Include more metadata in nuget package
- Also generate snupkg for native symbols.
  We intentionally don't add the symbols for native rust shared library
  to the nuget package since that could increase the size of the nuget.
  We will revisit that later.
- update licenses of all the bindings.

closes #551

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

bindings/java/pom.xml

@@ -18,7 +18,15 @@
   <licenses>
     <license>
       <name>MIT License</name>
-      <url>https://opensource.org/blog/license/mit</url>
+      <url>https://opensource.org/licenses/MIT</url>
+    </license>
+    <license>
+      <name>Apache License 2.0</name>
+      <url>https://www.apache.org/licenses/LICENSE-2.0</url>
+    </license>
+    <license>
+      <name>BSD 3-Clause License</name>
+      <url>https://opensource.org/licenses/BSD-3-Clause</url>
     </license>
   </licenses>