Python API: seek(eventtime)

[candlerb]

Is your feature request related to a problem? Please describe.
Feature-parity between APIs: Java Consumer and Reader have seek(messageId) and seek(timestamp), but Python has only seek(messageId) in Consumer, and nothing in Reader.

Describe the solution you'd like
Add a new method to Consumer and Reader to seek by timestamp. Or it could test the type of the value passed, or have different named arguments.

Describe alternatives you've considered
N/A

Additional context
Use cases are given in #5537 - e.g. rewind a reader to start at a given time.

[candlerb]

On further investigation I think some work on C++ API would be needed as well.

1. C++ API has seek in Consumer but not in Reader (which is where I want it)
2. Consumer::seek accepts only MessageId as its argument - although I see no reason why it can't be overloaded like its Java counterpart

In terms of the wire protocol, it would need to copy whatever the Java client does for seek(timestamp) - the command is built here.

[aahmed-se]

#5542