In the marker schema, add the ability to mark fields as hidden

[mstange]

Some markers have fields which shouldn't be displayed in the list of fields in the tooltip and in the sidebar.

We should have a way to mark these fields as hidden.

I know of three reasons for wanting to hide fields:

• If the field is already in the tooltip label / table label. See the section "Markers with fancy labels / tooltips" in Audit undeclared marker fields #5281 (comment) for examples.
• For markers with marker-based graphs, if the field is just used as a graph value, and there is another field which has the user-facing "readable" value. See the section "Markers with marker graphs" in Audit undeclared marker fields #5281 (comment) for examples.

#798 (comment) discusses a third reason why you might want to hide a field: If we supported tooltip entries of the type usage / capacity (full%), you wouldn't want a separate row for the capacity by itself.

┆Issue is synchronized with this Jira Task

[mstange]

Today, the way to use fields only in the tooltip or in graphs is to omit them from the schema. But we'll want to have all fields listed in the schema, to allow for future improvements to the profile storage format.

[mstange]

Also, today, if your tooltip label includes a field that's not listed in the schema, the field value must be a string, because you didn't write down the field format anywhere. For example it can't be a value in bytes.