Replace default CI test products with Core and Telegraf (#6812)

* feat(ci): add per-product codeblock testing with default group

- Add support for all products: core, enterprise, v2, v1, telegraf,
  cloud, cloud-dedicated, cloud-serverless, clustered, explorer
- Define default test group (core + telegraf) when no product specified
- Exclude cloud products from automatic CI (manual dispatch only)
- Add placeholder scripts for products without pytest services
- Normalize product name handling (core, influxdb3_core, influxdb3-core)
- Log informative messages when excluded products' content changes

* chore(ci): make codeblock tests manual-only and informational

- Remove pull_request trigger, keep only workflow_dispatch
- Change all exit codes to 0 so workflow never blocks PRs
- Use warnings instead of errors for failed tests
- Simplify job from detect-changes to parse-inputs

* feat(ci): make codeblock tests informational on PRs, manual-only execution

- PRs now trigger detection-only mode that suggests which products to test
- Actual test execution only runs via manual workflow_dispatch
- Add detect-test-products.js script using existing content-utils library
- Properly resolve shared content to affected product pages
- Non-blocking: PRs won't fail due to codeblock test issues

* Update .github/workflows/test.yml

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix(ci): add guard for empty products array after parsing

Co-authored-by: jstirnaman <212227+jstirnaman@users.noreply.github.com>

* fix(ci): remove redundant output before exit 1

Co-authored-by: jstirnaman <212227+jstirnaman@users.noreply.github.com>

---------

Co-authored-by: Jason Stirnaman <jstirnaman@influxdata.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jstirnaman <212227+jstirnaman@users.noreply.github.com>

Author: 3 people