chore(opentelemetry-node): switch to upstream instrumentation-openai

[trentm]

This swaps out '@elastic/opentelemetry-instrumentation-openai' for
'@opentelemetry/instrumentation-openai' now that it has been upstreamed.
The only visible changes to the user should be:

• the upstream instrumentation-openai has some slight improvements (made during the upstreaming), including adding support for instrumenting openai@5
• the 'openai' string can now be used in OTEL_NODE_DISABLED_INSTRUMENTATIONS et al
  (the usage of the old '@elastic/opentelemetry-instrumentation-openai' will be supported, with a log warning, until the next major)

Closes: #963
Refs: elastic/opentelemetry#450 (docs update)

[trentm]

• the usage of the old '@elastic/opentelemetry-instrumentation-openai' will be supported, with a log warning, until the next major

That looks like this:

% OTEL_NODE_DISABLED_INSTRUMENTATIONS=@elastic/opentelemetry-instrumentation-openai node --env-file ./test/test-services.env -r @elastic/opentelemetry-node test/fixtures/use-openai.js | pino-pretty
...
[14:09:56.739] WARN (elastic-otel-node): using "@elastic/opentelemetry-instrumentation-openai" in environment variable "OTEL_NODE_DISABLED_INSTRUMENTATIONS" is deprecated, use "openai"
...

Embeddings:
{
  object: 'list',
  data: [
    {
      object: 'embedding',
      embedding: [
           0.018015357,   -0.024581904,    0.02112887,     0.0360627,
          -0.035175975,   0.0065981457,   0.054628868, -0.0097577935,
...

[github-actions]

🔍 Preview links for changed docs

• docs/release-notes/index.md