Implicit specialisation: use regular array parameters for array constructors

Fixes compilation of test/timpfuncspez5 with LLVM and debug info, as the LLVM debug info writer internalerror's when you try to generate debug info for an array constructor (since those types should never appear as parameter/ variable types).

Replace them with reusable regular array types, so that multiple invocations of the same generic function with array constructors of the same type and number of elements are collapsed into the same specialisation