Require all marker fields to be listed in the schema

[mstange]

At the moment, markers can have fields in their data object without listing all fields in the marker schema. This only works because the current storage format is just a JSON object, where each value has a key. If we were to move to a format where we don't store the key for every field value for every marker, we need to first ensure that we don't have useful values stored in undeclared fields.

This is the tracking issue for that effort. We'll need to migrate all existing markers with undeclared fields via upgraders and via code paths in profile processing.

This bug can be resolved once all useful fields are declared in marker schemas, and once we can discard marker values for undeclared fields without anybody noticing.

┆Issue is synchronized with this Jira Task

[mstange]

#5281 has a list of cases of undeclared fields that we'll need to work through.