[BUG] Trace Span Parallel Execution Issue

[waleedlatif1]

Describe the bug
When we have workflows that have blocks that run in parallel, we see an incorrect trace span. Instead of seeing the blocks that ran concurrently at the same level, we see them nested within one another. This misrepresents the workflow order and doesn't accurately reflect to the user that those blocks ran in parallel.

To Reproduce
Steps to reproduce the behavior:

1. Go to workflow, create a workflow that executes two blocks in parallel
2. Click on logs icon in the sidebar
3. Navigate to the corresponding log for that workflow run and look at the trace span
4. Notice that the trace span is nested, despite those two blocks having ran in parallel

Expected behavior
Instead of the agent 1 and agent 2 being in parallel in the trace span, we see agent 2 being nested in agent 1 despite them being two separate calls that were executed in parallel.

Screenshots
Sample workflow that can be used to re-produce the bug:

Corresponding logs for the above workflow: