Don't send logs or traces for transport-otlp-http if their respective URLs are not defined

[pbhuynh]

Description

Currently, tracesURL and logsURL are both optional for @grafana/transport-otlp-http.

In our application, we only need traces so we don't have logsURL defined. However, the transport is still trying to send out resourceLogs to an undefined logsURL.

Steps to reproduce

import { getWebInstrumentations, initializeFaro } from '@grafana/faro-react';
import { OtlpHttpTransport } from '@grafana/faro-transport-otlp-http';

initializeFaro({
  // ...
  instrumentations: [
    // Load the default Web instrumentations
    ...getWebInstrumentations(),
  ],
  transports: [
    new OtlpHttpTransport({
      apiKey: env.faro.apiKey,
      // No logsURL defined
      tracesURL: 'https://example.com/v1/traces',
    }),
  ],
});

Expected behavior

If the url for the traces or logs endpoints aren't defined, then don't send the payloads.