Add schema support to Reader

[ZiyaoWei]

Master Issue: #344

Motivation

#368 adds support for schemas in consumer and producer, but didn't add the corresponding option to reader. This fixes that.

Modifications

Add schema field to ReaderOptions and pass the value to the consumer so messages can be read with a schema.

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

go test -run ^TestReaderWithSchema$ ./pulsar

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

• The public API: yes

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? GoDoc

[shoothzj]

@ZiyaoWei #748 is fixed, you can rebase the code for retrigger the ci

[wolfstudy]

+1