Use readonly or partitioned clients by default

[ca-johnson]

From brief discussion on #185

Using writeable clients is usually not necessary in CI and can cause performance regression for 'real' users as the db.have table becomes fragmented over time.

Partitioned is a more balanced choice, but readonly may be the best default to ensure that files being opened in the workspace during CI is always done with an understanding of the potential consequences. (i.e. we try to support this, but its not the default mode)

Make sure to bump major semver