feat: update observability documentation

[caalador]

Move old documentation under v4
Add migration documentation
and update references, configuration
and customization documents.

[github-actions]

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URL: https://docs-preview-pr-5769.fly.dev

Changed pages

Added content is highlighted in green; removed content is marked in red on each page.

• tools/observability — modified, +8/-5 lines, 3 removal marker(s)
• tools/observability/configuration — modified, +118/-142 lines, 42 removal marker(s)
• tools/observability/customization — modified, +244/-247 lines, 65 removal marker(s)
• tools/observability/getting-started — modified, +136/-51 lines, 29 removal marker(s)
• tools/observability/integrations — modified, +75/-13 lines, 10 removal marker(s)
• tools/observability/integrations/datadog — modified, +103/-94 lines, 41 removal marker(s)
• tools/observability/integrations/grafana — modified, +46/-63 lines, 18 removal marker(s)
• tools/observability/integrations/jaeger-prometheus — modified, +74/-56 lines, 25 removal marker(s)
• tools/observability/integrations/newrelic — modified, +44/-52 lines, 16 removal marker(s)
• tools/observability/integrations/prometheus — added, +94/-0 lines
• tools/observability/migrating-to-v5 — added, +340/-0 lines
• tools/observability/reference — modified, +246/-454 lines, 102 removal marker(s)

Other changed files

• articles/tools/observability/integrations/_run-app.adoc (deleted)

Built from 7e5a08d

[jouni]

Is there a need to keep the v4 documentation for Vaadin 25.2 docs? Could users simply access them in the Vaadin 24 docs?

[caalador]

Not really. It's there more for quick reference while working on the updated docs.

[heruan]

LGTM at the current state, final review when it's out of draft.

[ZheSun88]

the 1st alpha release for observability-kit v5 has been released with platform 25.3.0-alpha8.
remember to rebase this branch, if you need to modify the code or related content