Amazon DSP: add product/ASIN-level and audience-level reports#1943

Problem
The amazon_dsp connector currently covers order level (dsp_campaign), line item
level and creative level. Amazon’s DSP reporting also provides a product report
with an ASIN dimension and audience/segment reports. Our previous pipeline
delivered both. Without them the connector cannot fully replace it, so we would
have to keep the old pipeline running alongside Windsor.

Use cases

1. Attribute DSP spend and sales to individual ASINs. This is what our clients
   ask about in monthly reviews: which products the DSP budget actually moved.
2. Evaluate which audiences and segments drive purchases, in order to steer
   budget between them.

Scale reference
In our previous pipeline these reports carry roughly 200 columns (product) and
roughly 280 columns (audience). For a single mid-sized advertiser over eight
months that is about 330,000 product rows and about 700,000 audience rows, so
this is a substantial part of DSP reporting rather than a niche add-on.

Note
dsp_reach_frequency currently exposes only reach and frequency_average, which
does not cover audience reporting.

Done when
A dsp_product report with an asin dimension and a dsp_audience report are
available, delivered the same way as the existing DSP tables (same standard
technical columns, same destinations including BigQuery).