Playwright: Use new GH Pages actions

[sunker]

What this PR does / why we need it:

This PR uses the new actions to publish Playwright reports to Github Pages rather than uploading them as artifacts or deploying them to GCS.

Playwright tests running as part of plugin-e2e CI (playwright.yml)
Reports where at least one of the tests are now being deployed to GH Pages. A report comment is added to the PR with a summary of all the runs (see example at the bottom of this PR.

Scaffolded plugins
Like today, we don't want to upload reports as artifacts or deploy them to GH Pages automatically, as reports may include secrets (no directly after them being scaffolded, but if actively changed by plugin authors). For that reason, the necessary actions (upload-report-artifacts and deploy-report-pages) are added to the CI.yml workflow, however the upload-report is set to false meaning the report won't be uploaded to GH artifacts. While running tests as part of CI, a comment with a test result matrix will be added including a note describing how to enable publishing to GH pages.

Documentation

The example workflows showcased in the e2e CI docs are updated. There's also a detailed step by step instructions on how to add support for publishing reports. This will be useful for all plugins that have been scaffolded with an older version of create-plugin.

Example of this feature being used in external plugins:

Which issue(s) this PR fixes:

Fixes #1456

Special notes for your reviewer:

Since a while back, I've had a PR open to run e2e tests that run as part of create-plugin changes in two Grafana versions. I've updated this PR too so that it also publishes reports to GH actions.

📦 Published PR as canary version: Canary Versions

✨ Test out this PR locally via:

npm install website@3.6.0-canary.1504.c3ff863.0
npm install @grafana/create-plugin@5.15.0-canary.1504.c3ff863.0
# or 
yarn add website@3.6.0-canary.1504.c3ff863.0
yarn add @grafana/create-plugin@5.15.0-canary.1504.c3ff863.0

[github-actions]

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✨ This PR can be merged and will trigger a new minor release.
NOTE: When merging a PR with the release label please avoid merging another PR. For further information see here.

[sunker]

This means the report won't be uploaded to GH artifacts, and therefore not deployed to GH pages in the next job.

[github-actions]

Playwright test results

Image Name	Version	Result	Report
grafana-dev	11.6.0-221763	✅
grafana-enterprise	11.5.1	✅
grafana-enterprise	11.2.6	✅
grafana-enterprise	10.1.10	✅
grafana-enterprise	9.2.20	✅
grafana-enterprise	8.5.27	✅

Troubleshooting

404 when clicking on View report

By default, the deploy-report-pages Action deploys reports to the gh-pages branch. However, you need to take an extra step to ensure that GitHub Pages can build and serve the site from this branch. To do so:

1. Go to the Settings tab of your repository.
2. In the left-hand sidebar, click on Pages.
3. Under Source, select Deploy from a branch, then choose the gh-pages branch.

This action needs to be completed manually in order for your GitHub Pages site to be built and accessible from the gh-pages branch. Once configured, GitHub will automatically build and serve the site whenever new reports are deployed.