Error during simultaneous plugin execution

### Problem

An internal user reported that when two scheduled plugins execute at the same time, one of the two experiences an error:

> I have two different scheduled plugins accessing the same source database. One of them is an iceberg exporter, that runs every 5 minutes. The other is a downsampler than runs every 20 minutes. The downsampler runs fine with no errors. The iceberg exporter runs fine 3 times out of 4. When it runs at the same time as the downsampler plugin, it gets an error error: `generate_fields_string() missing 1 required positional argument: 'tags_list'`.
>
> If the iceberg export plugin runs when the downsampler plugin is not running, I don't get an error. It seems that there is some race condition when the two plugins run at the same time.
>
> I then changed the downsampler frequency to run every 10 minutes, and now the iceberg exporter runs without any problems but the downsampler gets an error `[ERROR] generate_fields_string() takes 2 positional arguments but 3 were given.`[^1]

So, it appears that scheduled plugins fire at the same time can interfere.

### Purpose of this issue

- [ ] Reproduce the above behaviour
- [ ] Investigate root cause
- [ ] See if we can fix it

[^1]: Internal Slack [thread](https://influxdata.slack.com/archives/C084G9LR2HL/p1755874770505469)