Add service.name attribute to metrics

[attilakreiner]

Description

This change adds the telemetry attribute service.name to the metrics attributes in the open telemetry exporter.

Fixes #1007

[jfallows]

Let's not introduce this separate metricsAttributes property and instead define service.name in attributes.

Then in otlp exporter, metrics can filter global telemetry attributes for presence of service.name and include it if present, otherwise omit.

This will let us specify the service.name and have it included in the exported metrics attributes as needed to fix the bug in the otlp demo.

Separately, @vordimous will define a story about enhancing our support for telemetry exporter attributes.

[vordimous]

@jfallows @attilakreiner, here is the ticket to track the additional changes to the telemetry attributes. We haven't decided if a global telemetry.attributes section is needed or if just an individual options.attributes section on each exporter will be better. The ticket includes both so that a decision can be made after some more discovery around implementation.

• Attribute support across telemetry exporters.  #1049

[attilakreiner]

Got it, done, pls chk @jfallows