feat: Runner image variants, CI improvements (#306)

## Description

Next step would be having full DE environment variant I guess? I'll see
later if it's doable in this PR or if I'll do separate one for keeping
things small and manageable for once 😅

- Added easily doable variants for runners, with simple CI build matrix.
- Added playsite in CI builds finally.
- Some CI formatting and naming fixes.
- Removed PR full runner builds as they kept failing due to lack of disk
space on GH runner.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* New dedicated runner images for Steam, Heroic, and Minecraft plus a
common runtime and builder images.
* **Chores**
* CI/workflow reorganization to build and publish more runner variants
and base images.
* Installer and package tweaks (package manager flags, CUDA enablement)
and updated build tooling.
* Unified startup to use a constructed launch command; removed two
default environment exports.
  * Added container ignore patterns.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: DatCaptainHorse <DatCaptainHorse@users.noreply.github.com>

.github/workflows/play-standalone.yml

@@ -0,0 +1,81 @@
+name: Build Nestri standalone playsite
+
+on:
+  pull_request:
+    paths:
+      - "containerfiles/playsite.Containerfile"
+      - ".github/workflows/play-standalone.yml"
+      - "packages/play-standalone/**"
+  push:
+    branches: [ dev, production ]
+    paths:
+      - "containerfiles/playsite.Containerfile"
+      - ".github/workflows/play-standalone.yml"
+      - "packages/play-standalone/**"
+    tags:
+      - v*.*.*
+  release:
+    types: [ created ]
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: nestrilabs/nestri
+  BASE_TAG_PREFIX: playsite
+
+jobs:
+  build-docker-pr:
+    name: Build image on PR
+    runs-on: ubuntu-latest
+    if: ${{ github.event_name == 'pull_request' }}
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+      - name: Setup Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Build Docker image
+        uses: docker/build-push-action@v5
+        with:
+          file: containerfiles/playsite.Containerfile
+          context: ./
+          push: false
+          load: true
+          tags: nestri:playsite
+
+  build-and-push-docker:
+    name: Build and push image
+    if: ${{ github.ref == 'refs/heads/dev' || github.ref == 'refs/heads/production' }}
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+      - name: Log into registry ${{ env.REGISTRY }}
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ github.token }}
+      - name: Extract Container metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}/${{ env.BASE_TAG_PREFIX }}
+          #
+          #tag on release, and a nightly build for 'dev'
+          tags: |
+            type=raw,value=nightly,enable={{is_default_branch}}
+            type=raw,value={{branch}}
+            type=raw,value=latest,enable=${{ github.ref == format('refs/heads/{0}', 'production') }}
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=semver,pattern={{major}}
+      - name: Build Docker image
+        uses: docker/build-push-action@v5
+        with:
+          file: containerfiles/playsite.Containerfile
+          context: ./
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}