modify RL examples to TF2 TL2

[quantumiracle]

Checklist

• I've tested that my changes are compatible with the latest version of Tensorflow.
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

Description

[zsdonghao]

Hi,

To correct the Python format automatically, run:
yapf -i xxx.py or yapf -i --recursive folder

Also, please put your name and PR ID in changelog.md, it will be listed in the next release.

[quantumiracle]

Hi,
I've cleaned the code and changed the log.

Thanks

[zsdonghao]

Let me know, when it is ready to be merged, but it seem that some conflicts must be solved before merging.