[FLINK-17118][python] Add Cython support for primitive data types

[HuangXingBo]

What is the purpose of the change

This pull request will support primitive DataTypes in Cython

Brief change log

• Use rmetzger/flink-ci:ubuntu-amd64-bcef226 image which contains gcc used for PyFlink cython tests
• Adds the file fast_coder_impl.(pyx,pxd) which includes the implementation of cython
• Add cython test environment in tox

Verifying this change

• Add correponding unit test in test_coders_common.py
• Add cython test environment in tox

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

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable)

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Automated Checks

Last check on commit ce14ff9 (Sun Apr 19 09:41:34 UTC 2020)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!

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• ❓ 1. The [description] looks good.
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• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

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CI report:

• ce14ff9 Travis: SUCCESS Azure: SUCCESS

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