Poetry support and refactor

Truegrequested to merge
poetry-support into main

Python projects have dependencies, mypy needs those dependencies to properly verify imported types. This means dependencies need to be installed, either via pip or poetry. This is not possible by injecting those dependencies into the kokkurri blubber build.

Thus, the kokkurri build has been removed in favor of manual installation into a venv. Apart from avoiding the build of a tmp docker image, this also means we can control the exact versions of the tools we use for linting (component parameters with defaults).

Bug: T426634

CC: @lerickson @gmodena

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