bigquery_reject_wildcard_metadata_source_freshness flag add suggestion on loaded_at_field

### Contributions

- [x] I have read the contribution docs, and understand what's expected of me.

### Link to the page on docs.getdbt.com requiring updates

https://docs.getdbt.com/reference/global-configs/bigquery-changes?version=2.0#the-bigquery_reject_wildcard_metadata_source_freshness-flag

### What part(s) of the page would you like to see updated?

Can we add the suggestion to use the [_TABLE_SUFFIX](https://docs.cloud.google.com/bigquery/docs/querying-wildcard-tables) field for the freshness when possible? This would save the user quite a bit of compute and money.

In a lot of cases, the table _TABLE_SUFFIX field will be transformable to a date, so then you can use it as a freshness field. And querying on a field in the table will do a full table scan, while _TABLE_SUFFIX is free for on-demand pricing and less slot time for slots..

### Additional information

_No response_