exhaust: added exhaust function, with stub for exhaust-csv-export and…

[pazbardanl]

… a sample impl

Types of changes

• Enhancement (project structure, spelling, grammar, formatting)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

A description of the changes proposed in the Pull Request

• added exhaust function
• added csv-exporter exhaust plugin

[narekhovhannisyan]

we should discuss if plugins are another repository or builtins

[narekhovhannisyan]

I think we got approval to import exhaust plugins as we are doing with ordinary plugins

[pazbardanl]

in retrospect i think this makes sense.

looking at the way ordinary plugins are being created from the manifest, i think applying a similar flow for creation of the exhaust plugins means significant changes relative to the PR state as it is right now.

i still think we should do it :) but maybe not in the scope of this task.
i propose maybe pushing the csv-export exhaust functionality as it is in this PR, and create a new issue (with the relevant priority) for refactoring it into external plugins. this actually means 2 PRs: one for IF exhaust infra and the other for a CSV exporter exhaust plugin.

The main reason im proposing it is that Joseph said in last weekly call he is very eager to be able to show the csv-export functionality.

WDYT?