Use YAML descriptions for Resources

[jsuereth]

Fixes #1399

Sending for feedback on approach.

Changes

• Update service + telemetry.sdk YAML to officially mark themselves as stable.
• Update snippet template to generate FULL resource semconv template, forcing all markdown to by in sync
• Add name to resource groups that denote the type field previously in markdown only.
• Add policy requiring naming conventions on name for resource group types.
• Add backwards compatibility check on resource - required/recommended attributes cannot be removed once stable.

Merge requirement checklist

• [x] CONTRIBUTING.md guidelines followed.
• [x] Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• [x] schema-next.yaml updated with changes to existing conventions.