chore: use uv caches (#32919)

Especially helpful for the text splitters tests where we're installing
pytorch (expensive and slow slow slow). Should speed up CI by 5-10 mins.

w/o caches, CI taking 20 minutes 😨 
w/ caches, CI taking 3 minutes

.github/actions/uv_setup/action.yml

@@ -1,12 +1,22 @@
-# TODO: https://docs.astral.sh/uv/guides/integration/github/#caching
-
 name: uv-install
-description: Set up Python and uv
+description: Set up Python and uv with caching
 
 inputs:
   python-version:
     description: Python version, supporting MAJOR.MINOR only
     required: true
+  enable-cache:
+    description: Enable caching for uv dependencies
+    required: false
+    default: 'true'
+  cache-suffix:
+    description: Custom cache key suffix for cache invalidation
+    required: false
+    default: ''
+  working-directory:
+    description: Working directory for cache glob scoping
+    required: false
+    default: '**'
 
 env:
   UV_VERSION: "0.5.25"
@@ -15,7 +25,13 @@ runs:
   using: composite
   steps:
     - name: Install uv and set the python version
-      uses: astral-sh/setup-uv@v5
+      uses: astral-sh/setup-uv@v6
       with:
         version: ${{ env.UV_VERSION }}
         python-version: ${{ inputs.python-version }}
+        enable-cache: ${{ inputs.enable-cache }}
+        cache-dependency-glob: |
+          ${{ inputs.working-directory }}/pyproject.toml
+          ${{ inputs.working-directory }}/uv.lock
+          ${{ inputs.working-directory }}/requirements*.txt
+        cache-suffix: ${{ inputs.cache-suffix }}