Turns on python-experimental CI tests, original

Created by: spacether

Turns on python-experimental CI tests

• pom.xml samples updated to indicate which node number corresponds to which set of samples
• circleci config file adjusted to allow a single node to use a different executor like docker for example

Reasons that I made these changes:

• the pyenv on the current machine is out of date and does not allow installation of new python versions >= 3.7
• to do that one would need build pyenv from scratch
• our current solution feels brittle and is not meeting the specific needs of the languages in a node. Everything is piled into one place
• How about we use docker images instead, built only for what we need? This PR demonstrates that by breaking out circleci node3 into a docker image with additional installations into it.

I have found a docker image which contains all python versions and will allow us to test python 2.7 all the way up to 3.9 which python-experimental needs. We will need to install the below into it:

• [DONE] maven
• [DONE] java jdk
• docker (to run the server)
• typescript/node for the other node3 tests

How about I make a dockerhub account for openapi generator which holds this new image? If we need to switch to other CI sites in the future, using this image should be easier than installing all needed software onto one machine like we currently do. Does this sound like a good plan to you? What email account can I use to make the dockerhub acccount for openapi generator (I don't want it to be my personal one)?

Help!

• I am having trouble installing docker in this Linux b2caa1cb8dfd 5.11.0-1022-aws #23~20.04.1-Ubuntu SMP Mon Nov 15 14:03:19 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux image

TODO:

• install docker in the running image
• run the server in the background of it
• turn the python-legacy samples tests back on
• install whatever typescript/node/angular and javascript need to run

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh

  Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master (5.3.0), 6.0.x
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