PYCBC-1775: Add GHA workflows for building & pruning performer images

Changes
=======
* Add GHA job for building performer images for every new tag, or push to master or release branches.
* Add GHA job for pruning stale temporary performer images. These are images built for a PR or Gerrit patch that are older than 7 days.

Change-Id: Ic032c88a3fcc7959a900159bc15e64aafa511eac
Reviewed-on: https://review.couchbase.org/c/couchbase-python-client/+/250544
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Jared Casey <jared.casey@couchbase.com>

Author: DemetrisChr

.github/workflows/prune-stale-images.yml

@@ -0,0 +1,25 @@
+name: Prune Stale Images
+
+on:
+  schedule:
+    - cron: '35 3 * * *'
+  workflow_dispatch:
+
+jobs:
+  prune:
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+
+    steps:
+      - name: Prune old temporary FIT performer images
+        uses: vlaurin/action-ghcr-prune@v0.6.0
+        with:
+          token: ${{ github.token }}
+          organization: ${{ github.repository_owner }}
+          container: python-fit-performer
+          keep-younger-than: 7 # days
+          prune-untagged: true
+          prune-tags-regexes: |
+            ^refs-
+            ^sha-

.github/workflows/publish-fit-performer.yml

@@ -0,0 +1,40 @@
+name: Publish FIT Performer
+permissions: {}
+
+run-name: ${{ inputs.ref }}
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ inputs.ref }}
+  cancel-in-progress: true
+
+on:
+  push:
+    branches:
+      - master
+      - release*
+
+    tags:
+      - '*'
+
+  workflow_dispatch:
+    inputs:
+      ref:
+        description: "Performer version. Specify a branch, tag, full commit hash, GitHub PR like 'refs/pull/37/merge', or Gerrit change like 'refs/changes/58/240858/6'"
+        required: true
+
+jobs:
+  publish:
+    name: Build & Publish Docker Image
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - uses: couchbaselabs/sdk-docker-build-action@v1
+        with:
+          sdk: python
+          ref: ${{ inputs.ref }}
+          dockerfile: ./tools/fit_performer/Dockerfile
+        env:
+          DOCKER_BUILD_SUMMARY: false