Implement ReconsumeLater on regex consumer

[jordanfitz]

Motivation

Currently, ReconsumeLater and ReconsumeLaterWithCustomProperties are unimplemented on regexConsumer. From what I can tell, these appear to just be missing methods rather than some fundamental limitation of the consumer implementation. Hopefully I'm correct there.

Modifications

I've essentially copied over the ReconsumeLaterWithCustomProperties implementation from multiTopicConsumer. I ran into the problem that the current code to add the RLQ topic to the consumer's Topics slice doesn't take into account subscriptions defined by TopicsPattern. To address this, I (perhaps naively) append the RLQ topic to the slice returned by regexConsumer.topics().

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• Added a test to ensure that a call to ReconsumeLater on a regex-based consumer causes the message to be published to the RLQ.

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

• Dependencies (does it add or upgrade a dependency): No
• The public API: No
• The schema: No
• The default values of configurations: No
• The wire protocol: No

Documentation

• Does this pull request introduce a new feature? No
• If yes, how is the feature documented? N/A
• If a feature is not applicable for documentation, explain why? The behavior of the newly-implemented method should be the same as the existing consumer implementations.