Activity Definition Upsert

[milt]

This PR illustrates a bug with SQL LRS where certain activity definition fields can be "forgotten" when multiple instances of an activity enter the LRS, one without a definition and one with. While the name and description fields appear to be preserved, the type field does not.

I've modified stmt-1 in the lrs tests to have an activity type to show the issue. Note that when stmt-0 (without a definition) precedes stmt-1 (with a definition), the resulting activity query is missing the type field. When it is the other way around, stmt-1 preceding stmt-0, the type field shows up.

The issue is resolved by updating the lrs lib's merge-activity function to allow updates to all definition fields, and to atomically update interaction activity fields.