OpenTelemetry metrics have no dimensions about emqx

[SergeTupchiy]

Note: traces briefly mentioned in the description do have some attributes, for example:

| 2024-01-30T10:15:28.527Z	info	TracesExporter	{"kind": "exporter", "data_type": "traces", "name": "logging", "resource spans": 1, "spans": 1}
| 2024-01-30T10:15:28.527Z	info	ResourceSpans #0
| Resource SchemaURL: 
| Resource attributes:
|      -> telemetry.sdk.name: Str(opentelemetry)
|      -> telemetry.sdk.language: Str(erlang)
|      -> telemetry.sdk.version: Str(1.4.7-emqx)
|      -> service.version: Str(5.5.0-g5007650b)
|      -> service.instance.id: Str([email protected])
|      -> service.name: Str(emqx)
|      -> process.runtime.name: Str(BEAM)
|      -> process.runtime.version: Str(14.1.1)
|      -> process.runtime.description: Str(Erlang/OTP 26 erts-14.1.1)
|      -> process.executable.name: Str(_build/emqx/rel/emqx/bin/emqx)
| ScopeSpans #0
| ScopeSpans SchemaURL: 
| InstrumentationScope emqx_opentelemetry 0.2.3
| Span #0
|     Trace ID       : aa13a024ca134a7cb4b41e048e8d28d1
|     Parent ID      : cef47eaa4ebc3fae
|     ID             : 1cfe6596235ef3e4
|     Name           : process_message
|     Kind           : Internal
|     Start time     : 2024-01-30 10:15:27.304084308 +0000 UTC
|     End time       : 2024-01-30 10:15:27.304366844 +000 UTC
|     Status code    : Unset
|     Status message : 
| Attributes:
|      -> messaging.destination.name: Str(t/trace)
|      -> messaging.client_id: Str(mqttx_8e7f0fb5)

There are Resource Attributes that can help identifying EMQX nodes (service.instance.id) and Attributes (topic and client id).

Metrics indeed don't have any attributes...