Construct ComponentArray from containers for keys and values

Hi,

My apologies if the following functionality already exists. In some cases, it might be convenient to construct a ComponentArray with a collection of keys and a collection of values. With this approach, you do not have to hard code the values into the constructor. NamedTuples provides this functionality:

using ComponentArrays

k = (:a,:b)
v = [1,2]
NamedTuple{k}(v)
(a = 1, b = 2)

Perhaps one annoyance is that the keys must be in a tuple. Using similar syntax, the returned object is a Vector{Int}

ComponentArray{k}(v)
An alternative syntax could be:

ComponentArray(k, v)

Start by checking the existing ComponentArray constructors and the NamedTuple behavior shown in the issue. Determine whether a keys-and-values constructor is supported or needs API design, then verify that the chosen form constructs the expected ComponentArray with the supplied keys and values.