Change the Chrome importer to emit schema-based markers

The Chrome importer currently creates markers whose `data.type` doesn't match a schema. Instead, we should have a schema and then set `data.type` to the name of the schema.

The `data` object also has other properties which need to be declared in a schema, for #5302.

In [this example profile](https://share.firefox.dev/4iPMqfc), most markers just have a `category` field. But some have a lot more data. You can find them by executing `filteredMarkers.filter(m => m.data && Object.keys(m.data).length > 2)` on the console.

I'm not sure what to do about that extra data. It could be stuffed in a field called `chromeMarkerData` with a new field format called `freeform-object`.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-858)