[CHORE]: Update map trace `fitbounds` attribute to be enum instead of boolean

[camdecoster]

Description

Update the map trace fitbounds attribute to be an enum instead of boolean.

Why should this change be made?

This will allow us to treat fitbounds in a similar way to the corresponding attribute for geo traces. Right now the auto-fit for map traces skips choropleths because those would have to be handled at a different point in the code. As such, the attribute could just be on/off. If we add choropleth support in the future, the attribute schema will have to change. By making this change now before the release of v4.0, we won't have to worry about breaking anything.

Scope

• Update the attribute
• Update the schema and types

Notes

• A user introduced a PR (Add fitbounds support for map subplots #7911) that adds fitbounds to map traces, but it's built against master instead of v4.0
• I'd like to make this change and then ask the user to adapt their PR to the v4.0 changes