AVRO-3224: Fix ReflectDatumReader.readField when using ReflectData.AllowNull with two conversions that convert to the same avro logical type

[liu-du]

Make sure you have checked all steps below.

Jira

• [x] My PR addresses the following Avro Jira issues and references them in the PR title. For example, "AVRO-1234: My Avro PR"
  • https://issues.apache.org/jira/browse/AVRO-3224

Tests

• [x] My PR adds the following unit tests:
  • TestReflectLogicalTypes.testReflectedSchemaWithMultipleDateConversions
  • TestReflectLogicalTypes.testReflectedSchemaWithMultipleDateConversions

Commits

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  4. Subject uses the imperative mood ("add", not "adding")
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  6. Body explains "what" and "why", not "how"

Documentation

• No new functionality

[liu-du]

@opwvhk

I changed the code a bit so now it's able to handle array of unions as well. Also the logic of apply logical conversions are now removed into one place in ReflectDatumReader.readAndConvert. Could you help review again? Thank you

[opwvhk]

Looks a lot better now! Thank you. I've left a few minor remarks which I think would make it even better, but other than that it looks good to me.

[liu-du]

I've changed the code according to the remarks. Thank you for the review!