tests: have coins simulation test also use CCoinsViewDB

Summary:

Before this change, the coins simulation test uses a base view of type
CCoinsViewTest, which has no relevance outside of the unittest suite. Might as
well reuse this testcase with a more realistic configuration that has
CCoinsViewDB at the bottom of the view structure.

This is a backport of Core PR17669

Test Plan: ninja && ninja check

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8936