Do not allow callconv, align, addrspace, or linksection to reference function arguments

[mlugg]

Split out from #11834.

Allowing these things to reference previous parameters requires the compiler implementation to track all of these properties in more places, increasing memory consumption. It also requires the compiler to have a separate representation of these properties for functions vs other declarations.

Another implementation problem with callconv in particular, originally mentioned in #11834, is that status quo can lead to us finding out that a function should be inlined (due to having callconv(.@"inline")) after analyzing its arguments, which is too late -- we've already started creating a generic instantiation! (Admittedly, though, this problem still exists -- and likely always will exist -- for the case of a return type turning out to be comptime-only.)

There isn't much point in actually allowing this; you'd have to be deep in generic crazy land to be affected by this change, and if you really need it, you can wrap your whole function in a generic type. Therefore, this proposal is to disallow the bodies of callconv(...), align(...), addrspace(...), and linksection(...) on function bodies from referring back to function parameters.