Static array with non-obvious element type

[straight-shoota]

When creating a static array with StaticArray.[] macro, the generic element type argument is inferred from the union of all macro argument types. However, there might be use-cases where the element type of the static array differs from the union of it's initial elements. This cannot be expressed using the [] macro.
As a workaround you need to use one of the constructors and assign the elements manually. It's more verbose but works. I'm not sure if this necessarily needs to change.

StaticArray#to_s and #pretty_print both stringify an instance as StaticArray[<element>] which suggests that this string representation can be used as a literal-like expression in source code representing the exact same value. But this is only the case is if T equals the union of all value types.
At least #pretty_print (and #inspect) should probably be more specific here because inspecting a static array should show the exact type. This could be improved by changing the print output to include T (for example StaticArray(Int32 | Float64)[1, 2, 3]) at least when it differs from the union of element types. However, this won't be usable in Crystal code because it is not a valid expression.

[jhass]

Can we make StaticArray(String, 2) {"a", "b"} work and switch inspect to that? https://carc.in/#/r/7ldf

[straight-shoota]

Related to #5703