Remove OTel resources and drop `contexts.otel.resource`

[andreiborza]

In v11 the default (and, after JS-2585, only) tracer provider is SentryTracerProvider, which runs no OTel SDK export pipeline. The OTel resource is no longer meaningful and should be removed.

• Drop getSentryResource / packages/opentelemetry/src/resource.ts (or reduce it to what's still needed)
• Stop attaching contexts.otel.resource to transaction events (packages/node/src/sdk/initOtel.ts:169-176)
• Remove the resource passed to SentryTracerProvider in initOtel.ts
• This eliminates the @opentelemetry/core SDK_INFO import in resource.ts:2 (last core import besides SentryPropagator)
• v11 migration note: contexts.otel.resource (incl. telemetry.sdk.*) no longer attached to events

Relates to JS-2585 (removes the options that force the full OTel SDK provider) and JS-2820 (SentryPropagator removal). Together these remove the last direct @opentelemetry/core imports from @sentry/opentelemetry, unblocking JS-2929 (peer removal).

[linear-code]

JS-2930