Adjust to refactoring of specifications (Q3-Q4)

[chalin]

• Move spec-status page to be immediately under /docs/specs #2796
• CODEOWNERS: add specs-approvers to /docs/specs #2797
• Adjust to move of OTLP specs into opentelemetry-proto #2642
  • Get OTLP status from OTLP spec #2794 fixes spec_status failure. See the PR for details
  • Link to OTLP spec #2799
• Add OpAMP spec to the specs list #2795
• Ensure that OTel spec appears first among the specs #2928
• Adjust to move Semantic Conventions out of OTel spec #2721
• OTel spec:
  • [editorial] Add Hugo front-matter for protocol to match OTLP pages opentelemetry-specification#3552
  • [editorial] Ensure trace subsections have a README opentelemetry-specification#3553
  • [editorial] Data model appendix: table-entry markdown and typo fixes opentelemetry-specification#3571
  • [CI/editorial] Report link-check error when external URL used for local spec page opentelemetry-specification#3591
  • [editorial] Hugo front-matter fixes for aliases and linkTitle opentelemetry-specification#3592
  • Update spec submodule to bring in the above editorial changes.
• OTLP spec updates:
  • [editorial] spec: escape HTML chars in markdown link syntax opentelemetry-proto#487
  • Update spec submodule to bring in the above editorial changes.
• OpAMP
  • [editorial] Update spec to make it suitable for publication on the OTel website opamp-spec#148
  • Update OpAMP to latest and stop using relref for it #3391
  • OpAMP spec adjustments #2927
  • Update spec submodule to bring in the above editorial changes.
• Update to spec 1.26.0 and semconv 1.22.0 at the SAME time #3388
• Post specs update: address 404s and reenabled all checks #3392