[SL-2777] Reproduce error with conversion metric and missing group by

@courtney.holcomb said:

> We've been seeing [this error](https://dbt-labs.slack.com/archives/C050Z6UP4RK/p1724265046998049) come up in the logs a lot lately, and I was finally able to repro. It's triggered by querying a conversion metric with a where filter but with no group by. The where filter is only applied to one of the measures, so then we aren't able to join the two aggregated measures. I'm not super familiar with conversion metric behavior. What do we want the experience to be in that scenario to fix this bug? cc @willymwai.deng @jordan.stein
>
> \[August 21st, 2024 11:30 AM\] diego.fernandez: Hey all, we've seen this error a few times in MFS recently:
> `All parent nodes should have the same set of linkable instances since all values are coalesced.`
> They all seem to come from the same account, so maybe it's a configuration error on their side, but it shows up as errors on our side <[https://dbtlabsmt.datadoghq.com/logs?query=%40extra.job.error.message%3A"All parent nodes should have the same set of linkable instances since all values are coalesced."&agg_m=count&agg_m_source=base&agg_t=count&cols=host%2Cservice&context_event=AZFy6QYvAAC7NuVb965U8ACb&fromUser=false&graphType=flamegraph&historicalData=true&hostGroup=\*&lens=Performance&messageDisplay=inline&page=1&panelFrom=1724209200000&panelStorageType=hot&panelTo=1724210400](https://dbtlabsmt.datadoghq.com/logs?query=%40extra.job.error.message%3A%22All%20parent%20nodes%20should%20have%20the%20same%20set%20of%20linkable%20instances%20since%20all%20values%20are%20coalesced.%22&agg_m=count&agg_m_source=base&agg_t=count&cols=host%2Cservice&context_event=AZFy6QYvAAC7NuVb965U8ACb&fromUser=false&graphType=flamegraph&historicalData=true&hostGroup=%2A&lens=Performance&messageDisplay=inline&page=1&panelFrom=1724209200000&panelStorageType=hot&panelTo=1724210400)...

_{From [SyncLinear.com](https://synclinear.com) | [SL-2777](https://linear.app/dbt-labs/issue/SL-2777/reproduce-error-with-conversion-metric-and-missing-group-by)}