otelgrpc: add WithSpanOptions behavior to stats_handler

[josepedropereira]

Problem Statement

otelgrpc stats_handler does not support the config SpanStartOptions, even tho this config is supported in the deprecated interceptors since #3768

Proposed Solution

Append SpanStartOptions to the stats_handler SpanStartOptions like it's done on the interceptors side to have the same functionality for both use cases.

[pellared]

From #5251 (review):

I am not sure if it is good to allow users to do that much.

The user can e.g. change the span kind using https://pkg.go.dev/go.opentelemetry.io/otel/trace#WithSpanKind or create attributes which are not aligned with the semantic conventions and they others may blame that the instrumentation library does not follow semantic conventions.

so folks can (for example), enable stack traces to record errors.

I am not sure if this is a good justification. This instrumentation library is not recording any errors.

I think we can discuss during the SIG meeting if we should make instrumentation libraries so configurable.

I am aware that there is a precedent that otelhttp and otelgrpc already have WithSpanOptions but maybe we should retrospect this.