Provide API to transform SpanScope into TelemetryContext. That allows ergonomically apply span scopes returned by start_trace to futures. In addition, it allows us to get rid of TelemetryContext::apply_with_tracing_span and alike
Add telemetry instrumentation support for !Send futures
SpanScopeintoTelemetryContext. That allows ergonomically apply span scopes returned bystart_traceto futures. In addition, it allows us to get rid ofTelemetryContext::apply_with_tracing_spanand alike!Sendfutures#[allow(dead_code)](closes https://github.com/cloudflare/foundations/issues/39)