Use pysqlite3 instead of sqlite3 to allow for support of upsert syntax in Python 3.7

[rmitsch]

Description

The weekly build currently fails on BuildKite to the usage of Python 3.7 and the sqlite3 version shipped with it due to its lack of support of the SQLite upsert syntax uses in the NEL benchmark project. Since upgrading sqlite3 isn't easily possible independent from the Python installation itself, this PR replaces sqlite3 with the drop-in support pysqlite3.

Checklist

• [x] I confirm that I have the right to submit this contribution under the project's MIT license.
• [x] I ran the tests, and all new and existing tests passed.
• [x] My changes don't require a change to the documentation, or if they do, I've added all required information.