OpAMP spec adjustments

[chalin]

• [editorial] Update spec to make it suitable for publication on the OTel website opamp-spec#148
• Ensure that OTel spec is first in specs list --> Ensure that OTel spec appears first among the specs #2928
• Replace link to https://github.com/open-telemetry/opentelemetry-specification/tree/main/specification/resource/semantic_conventions by path to semconv page.
  • Note that this link breaks the page on mobile (since the link is too wide to be displayed within the page width)
  • [editorial] Fix link to Resource Semantic Conventions opamp-spec#156
• [editorial] Add missing [Beta] markdown link definition + copyedit opamp-spec#158
• [editorial] Drop period after "Status: [Beta]" opamp-spec#159
• Update opamp-spec and drop script workarounds #3006
• [editorial] spelling correction in specification.md opamp-spec#155
• Update opamp-spec, bringing in spelling fixes #3014
• [editorial] Spec: replace links to semantic_conventions by semconv section of OTel website  opamp-spec#150
• Update opamp-spec submodule #3039
• [editorial] Normalize spec-local cSpell words opamp-spec#163
• Ensure page displays properly on mobile
• Propose unindenting diagrams and using goat to render nicer figures (CSS will need to be adjusted)
• Update OpAMP spec submodule
  • Update OpAMP to latest and stop using relref for it #3391