Adds support for KSqlDB session variables

[nachomdo]

• Please check if the PR fulfills these requirements

• The commit messages are descriptive
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• An issue has been created for the pull requests. Some issues might require previous discussion.

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  Feature - KSqlDB Session Variables support to enable parametric artefacts  #545

• What is the current behavior? (You can also link to an open issue here)
  KSqlDB Session Vars are not supported

• What is the new behavior (if this is a feature change)?
  Allows to specify session vars that can be interpolated in parametric KSqlDB artefacts

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No breaking changes. Session vars can be safely omitted from the topology descriptor file

• Other information:
  Upgrade of KSqlDB container and API client to versions that support the definition of session vars.
  Upgrade of Zookeeper client due to conflicts with Netty dependencies

[purbon]

I like it, thanks a lot @nachomdo for your contribution. I'm in the process of merging this in, it will be available in the next upcoming release.