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>

libs/langchain/dev.Dockerfile

@@ -14,10 +14,14 @@ ARG PYTHON_VIRTUALENV_HOME=/home/vscode/langchain-py-env \
 ENV POETRY_VIRTUALENVS_IN_PROJECT=false \
     POETRY_NO_INTERACTION=true 
 
-# Create a Python virtual environment for Poetry and install it
+# Install Poetry outside of the v`irtual environment to avoid conflicts
+RUN python3 -m pip install --user pipx && \
+    python3 -m pipx ensurepath && \
+    pipx install poetry==${POETRY_VERSION}
+
+# Create a Python virtual environment for the project
 RUN python3 -m venv ${PYTHON_VIRTUALENV_HOME} && \
-    $PYTHON_VIRTUALENV_HOME/bin/pip install --upgrade pip && \
-    $PYTHON_VIRTUALENV_HOME/bin/pip install poetry==${POETRY_VERSION}
+    $PYTHON_VIRTUALENV_HOME/bin/pip install --upgrade pip
 
 ENV PATH="$PYTHON_VIRTUALENV_HOME/bin:$PATH" \
     VIRTUAL_ENV=$PYTHON_VIRTUALENV_HOME