Connect State::apply_block to parent span from StoreApi::apply_block

[sergerad]

The apply_block call at block_producer.rs:115 runs inside a tokio::spawn, which detaches it from the parent gRPC span. The #[instrument] on State::apply_block at apply_block.rs:44 creates a new root span rather than being a child of the caller's trace.

    // TODO: This span is logged in a root span, we should connect it to the parent span.
    #[expect(clippy::too_many_lines)]
    #[instrument(target = COMPONENT, skip_all, err)]
    pub async fn apply_block(

To fix it, we need to capture the parent span context before spawning and pass it into the spawned task (e.g., via tracing::Span::current() or by propagating the OpenTelemetry context manually).

[sergerad]

@Mirko-von-Leipzig please sanity check this issue description for me 🙏