avro

AVRO-3518: Introduce a new type 'Alias' (#1686)

It uses Newtype pattern and wraps Name. This way it is easier to control
how it is being (de)serialized

Until now only Schema::Record serialized its aliases to JSON. Now this
is being done for all named schemata (Schema::Enum and Schema::Fixed)

Signed-off-by: Martin Tzvetanov Grigorov <mgrigorov@apache.org>