Remove extra label value types

[jtescher]

Currently label value types can include INT32, UINT32, UINT64, and FLOAT32 values, but the spec states that:

An Attribute MUST have the following properties:
...
The attribute value, which is either:
* A primitive type: string, boolean, double precision floating point (IEEE 754-1985) or signed 64 bit integer.
* An array of primitive type values. The array MUST be homogeneous, i.e. it MUST NOT contain values of different types.

Should we remove the extra values that are not compliant?

[MrAlias]

I like the idea of reducing the API surface area and conforming to the specification. 👍

[dstdfx]

@MrAlias would be glad to take this one