Series type

[kylebrandt]

• Depends on dataframe: method to get underlying type of Vector grafana-plugin-sdk-go#24 getting merged at tagged with release.

[kylebrandt]

Basic Idea: non-pointer type is a proper subset its pointer type (nullable type), i.e. float64 ⊂ *float64

• Series gets a nullableTime property which reflects if the time Vector is a slice time.Time or *time.Time.
• Getters always return pointers
• Setters always take pointers, and set the appropriate type (will error if an attempt to set nil to a series with non null-nullable.
• nonPointer Op nonPointer = nonPointer, pointer Op nonPointer = pointer (or switched), pointer Op pointer = pointer

Is this actually what I did ...

[kylebrandt]

Needs sdk pr merged, then this updated

[kylebrandt]

I don't know that it is fair to ask for a review on this ... is quite large, moved some tests around. This tests are still a mess, I need to make a scenario matrix of some sort and figure out how they should be structured. Currently just continuing some debt.

I think after Frame.Labels -> Frame.Field.Labels is probably a good time to do that.

Main changes are type_series. Some TODOs are left in there but I am okay with that.