ci: add new action to install ollama, cache the model (#2054)

# What does this PR do?
This PR introduces a reusable GitHub Actions workflow for pulling and
running an Ollama model, with caching to avoid repeated downloads.

[//]: # (If resolving an issue, uncomment and update the line below)
Closes: #1949 

## Test Plan

1. Trigger a workflow that uses the Ollama setup. Confirm that:
- The model is pulled successfully.
- It is placed in the correct directory, official at the moment (not
~ollama/.ollama/models as per comment so need to confirm this).
2. Re-run the same workflow to validate that:
- The model is restored from the cache.
- Execution succeeds with the cached model.

[//]: # (## Documentation)

.github/actions/setup-ollama/action.yml

@@ -0,0 +1,26 @@
+name: Setup Ollama
+description: Start Ollama and cache model
+inputs:
+  models:
+    description: Comma-separated list of models to pull
+    default: "llama3.2:3b-instruct-fp16,all-minilm:latest"
+runs:
+  using: "composite"
+  steps:
+    - name: Install and start Ollama
+      shell: bash
+      run: |
+        # the ollama installer also starts the ollama service
+        curl -fsSL https://ollama.com/install.sh | sh
+
+    # Do NOT cache models - pulling the cache is actually slower than just pulling the model.
+    # It takes ~45 seconds to pull the models from the cache and unpack it, but only 30 seconds to
+    # pull them directly.
+    # Maybe this is because the cache is being pulled at the same time by all the matrix jobs?
+    - name: Pull requested models
+      if: inputs.models != ''
+      shell: bash
+      run: |
+        for model in $(echo "${{ inputs.models }}" | tr ',' ' '); do
+          ollama pull "$model"
+        done

.github/workflows/integration-tests.yml

@@ -38,19 +38,8 @@ jobs:
           python-version: "3.10"
           activate-environment: true
 
-      - name: Install and start Ollama
+      - name: Setup ollama
-        run: |
+        uses: ./.github/actions/setup-ollama
-          # the ollama installer also starts the ollama service
-          curl -fsSL https://ollama.com/install.sh | sh
-
-      # Do NOT cache models - pulling the cache is actually slower than just pulling the model.
-      # It takes ~45 seconds to pull the models from the cache and unpack it, but only 30 seconds to
-      # pull them directly.
-      # Maybe this is because the cache is being pulled at the same time by all the matrix jobs?
-      - name: Pull Ollama models (instruct and embed)
-        run: |
-          ollama pull llama3.2:3b-instruct-fp16
-          ollama pull all-minilm:latest
 
       - name: Set Up Environment and Install Dependencies
         run: |