[cmd/telemetrygen] Change span kind from an attribute to top level info

[edwintye]

Description: Remove the span attribute span.kind and instead set the Kind (which is a top level span information) directly using trace.WithSpanKind.

Link to tracking Issue: #24286

Testing: Added a rudimentary test to ensure that Kind is not Internal which is the default when not specified.

Documentation: None. This is probably the original intention.

[codeboten]

Thanks for opening this, one change needed

[codeboten]

Please add a changelog and we can get this merged 👍🏻

[edwintye]

Added a chlog entry and rebased, looks like a couple tests fails but seems unrelated to my untrained eyes.

[mx-psi]

@edwintye this one does need addressing on this PR:

telemetrygen/internal/traces/worker_test.go:8: File is not `gci`-ed with --skip-generated -s standard -s default -s prefix(github.com/open-telemetry/opentelemetry-collector-contrib) (gci)
	"go.opentelemetry.io/otel/trace"
telemetrygen/internal/traces/worker_test.go:15: File is not `gci`-ed with --skip-generated -s standard -s default -s prefix(github.com/open-telemetry/opentelemetry-collector-contrib) (gci)
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
telemetrygen/internal/traces/worker_test.go:11: File is not `goimports`-ed with -local github.com/open-telemetry/opentelemetry-collector-contrib (goimports)