Implement SQLiteDatabase::Open

Summary:
This is a backport of core#19077 [7/26]
https://github.com/bitcoin/bitcoin/pull/19077/commits/a0de83372be83f59015cd3d61af2303b74fb64b5

Depends on D10546

Note: this uncomments the previously unused member vars m_mock (D10542) and m_database (D10545)

Test Plan:
With clang-tidy:
ninja

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10547