feat(conda): share envs with transformer-based backends (#1465)

* feat(conda): share env between diffusers and bark

* Detect if env already exists

* share diffusers and petals

* tests: add petals

* Use smaller model for tests with petals

* test only model load on petals

* tests(petals): run only load model tests

* Revert "test only model load on petals"

This reverts commit 111cfa97f1.

* move transformers and sentencetransformers to common env

* Share also transformers-musicgen

backend/python/common-env/transformers/install.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+set -ex
+
+# Check if environment exist
+conda_env_exists(){
+    ! conda list --name "${@}" >/dev/null 2>/dev/null
+}
+
+if conda_env_exists "transformers" ; then
+    echo "Creating virtual environment..."
+    conda env create --name transformers --file $1
+    echo "Virtual environment created."
+else 
+    echo "Virtual environment already exists."
+fi