Variable schema for postgressql output plugin

### Use Case

I have a PostgresSQL DB with several schemas. schemaA, schemaB, etc., in which I feed data from sensors through the mqtt_consumer plugin.

After a bit of processing, the measurement names look like
"correspondingSchema_sensorName"

### Expected behavior

I would like to be able to set the schema-name from a tag, which I would drop afterwards.

### Actual behavior

Right now I have to define several outputs, one for each schema:

```
[[outputs.postgresql]]
namepass = ["schemaA_*"]
schema = "schemaA"

[[outputs.postgresql]]
namepass = ["schemaB_*"]
schema = "schemaB"
```

### Additional info

_No response_

Start at the outputs.postgresql plugin configuration and schema handling, then inspect how tags from mqtt_consumer are represented and can be removed. Define how a tag-selected schema should work for each measurement and verify the behavior with the plugin's existing tests or configuration checks; the issue names no files or tests.

Written by the indexing model from the issue text.