Use destructuring syntax once we establish Julia v1.7 as the base

[dmbates]

I often start functions by extracting fields from, e.g. a LinearMixedModel struct and Julia v1.7 introduces the destructuring syntax

• (; a, b) = x can now be used to destructure properties a and b of x.
  This syntax is equivalent to a = getproperty(x, :a); b = getproperty(x, :b) ([#39285]).

[palday]

That's some nice syntax. 😄

If 1.6 is declared LTS, then we should only do this if Compat.jl provides a way to support it.