[FLINK-23589][flink-avro] Support microsecond precision for timestamp

[matriv]

What is the purpose of the change

Add support for microsecond precision for timestamp in Avro.

Brief change log

• Add support for microsecond precision for timestamp in AvroRowDataDeserializationSchema.
• Adjust tests to use different digits for hours:mins:seconds
• Adjust tests to use complete timestamp and time when testing micros

Verifying this change

This change added tests and can be verified as follows:

• AvroRowDataDeSerializationSchemaTest#testSpecificType
• Adjusted all other tests to use full data/time when testing timestamp/time with micros

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable