`OTEL_RESOURCE_ATTRIBUTES` parsing has whitespace in keys

We run all of our services in Kubernetes, and define our open telemetry resource attributes like so:

            - name: OTEL_RESOURCE_ATTRIBUTES
              value: >
                service.name=redacted,
                service.version=redacted,
                k8s.node.name=$(KUBE_NODE_NAME),
                k8s.pod.name=$(KUBE_POD_NAME),
                k8s.pod.uid=$(KUBE_POD_ID),
                k8s.namespace.name=$(KUBE_NAMESPACE)

All of our other services (java, python) seem to split on "=" and then clean up whitespace in the key, but unfortunately the ruby library sends over service.version=redacted (note the whitespace in front of the key).

Looks like the problem is here: https://github.com/open-telemetry/opentelemetry-ruby/blob/main/sdk/lib/opentelemetry/sdk/resources/resource.rb#L47-L50

Start in sdk/lib/opentelemetry/sdk/resources/resource.rb at the parsing logic around lines 47–50. Reproduce the issue with the multiline OTEL_RESOURCE_ATTRIBUTES value shown, then verify that parsed attribute keys do not retain leading whitespace. Done when the corrected parsing behavior is covered by the relevant tests.