remaining uses of pip in poetry

* installation of the managed package, when that package has a build script: [here](https://github.com/python-poetry/poetry/blob/43dd8cce4f04120ee698609fa0a0a66063e80dcd/src/poetry/masonry/builders/editable.py#L102)

* uninstalling packages: [here](https://github.com/python-poetry/poetry/blob/43dd8cce4f04120ee698609fa0a0a66063e80dcd/src/poetry/installation/executor.py#L592)

desirable to remove both of these in the long run...

Hi! Are there issues filed for removing these two usages of invoking pip? I tried searching but there are 200+ results for "pip" (and filtering further was a bit hit or miss):
https://github.com/python-poetry/poetry/issues?q=is%3Aissue+is%3Aopen+pip

If you would like to contribute please just go ahead, no need for ceremony.

Some hints here

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