infra: fix how Poetry is installed in the dev container (#20521)
Currently, when a new dev container is created, poetry does not work in
it with the error "No module named 'rapidfuzz'".
Install Poetry outside the project venv so that poetry and project
dependencies do not get mixed. Use pipx to install poetry securely in
its own isolated environment.
Issue: #12237
Twitter handle: https://twitter.com/ibratoev
Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>