[Enhancement] Optimize DefaultMQProducer construction method

[yx9o]

Before Creating the Enhancement Request

• I have confirmed that this should be classified as an enhancement rather than a bug/feature.

Summary

I found a duplicate structure in the constructor.

Motivation

To reduce code duplication and improve code reusability.

Describe the Solution You'd Like

We can let one constructor call another constructor, and finally perform the actual assignment operation only in one constructor.

Describe Alternatives You've Considered

In each constructor, directly call the most complete constructor.

Additional Context

No response