Static Viz and Exports/Downloads Respect Dashcard Viz Settings (#45164)

* start adding some util fns to download-exports-test ns

* wip improving test util fns

* add subscription attachment util fn

* add tests to catch download/export differences

* viz-settings from card and dashcard  merged properly

* revert these changes which probably aren't needed

* split test: downloads can be parallel, email attachments cannot

* normalize viz-settings no matter their origin

* Update test/metabase/api/downloads_exports_test.clj

Co-authored-by: Alexander Solovyov <alexander@solovyov.net>

* Incorporate some review feedback

* rendered table cards also respect column names

* Clean up table render tests and remove unhelpful render test utils

The big removal of code in the render test utils namespace is a clean up task that could've happened sooner, but this
table test adjustment is the perfect opportunity to clean up.

I had made the test utils before I truly knew how best to use `mt/with-temp`, so it had a lot of poorly implemented
'generators' that were doing a poor job of creating mock data for the rendering functions anyway.

So, reworking a few table tests here to just use a temp card is way more inline with the rest of the codebase, and
actually improves confidence that the tests are testing on well-formed data to begin with.

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Co-authored-by: Alexander Solovyov <alexander@solovyov.net>