consider adding @fastify/otel instrumentation

[trentm]

• Soonish instr-fastify will no longer be getting new versions (and will be removed from auto-instrumentations-node). We should drop it.
• Consider adding @fastify/otel, the blessed community replacement.
• We could have the new one get enabled via explicit fastify in OTEL_NODE_ENABLED_INSTRUMENTATIONS, or require explicit clear @fastify/otel name. I lean towards the latter for clarity. Having "fastify" in there "just work" migh be misleading because the instr is different.
• If we add @fastify/otel are there going to be dep duplicates to worry about? E.g. otel/instr version. We could perhaps use overrides... or just engage upstream.
  • At time of writing it has the latest @opentelemetry/instrumentation on main, but hasn't had recent releases.