Merge #17669: tests: have coins simulation test also use CCoinsViewDB

bee88b8c5887e6beb75f26f0db97888a48fa7e7c tests: have coins simulation test also use CCoinsViewDB (James O'Beirne)

Pull request description:

  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 (i.e. in-memory leveldb) at the bottom of the view structure.

  This adds explicit use of CCoinsViewDB in the unittest suite.

  #### Before change
  ```
  ./src/test/test_bitcoin --run_test=coins_tests --catch_system_errors=no  21.99s user 0.04s system 99% cpu 22.057 total
  ```

  #### After change
  ```
  ./src/test/test_bitcoin --run_test=coins_tests --catch_system_errors=no  78.80s user 0.04s system 100% cpu 1:18.82 total
  ```

ACKs for top commit:
  ryanofsky:
    Code review ACK bee88b8c5887e6beb75f26f0db97888a48fa7e7c

Tree-SHA512: 75296b2bcbae2f46e780489aafb032592544a15c384d569d016005692fe79fe60d7f05857cf25cc7b0f9ab1c53b47886a6c71cca074a03fb9afec30e1f376858

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