fix(cmake): record avro-cpp as system dependency in installed config (#987)

The installed iceberg-config.cmake called find_dependency(Avro), but the package found is avro-cpp, which does not provide an Avro package. Closes #973

Co-authored-by: Rohan Jain <rohanjain@microsoft.com>

Author: rohanjain101

cmake_modules/IcebergThirdpartyToolchain.cmake

@@ -350,7 +350,7 @@ function(resolve_avro_dependency)
     endif()
   else()
     set(AVRO_VENDORED FALSE)
-    list(APPEND ICEBERG_SYSTEM_DEPENDENCIES Avro)
+    list(APPEND ICEBERG_SYSTEM_DEPENDENCIES avro-cpp)
   endif()
 
   set(ICEBERG_SYSTEM_DEPENDENCIES