Tighten validation of hvncat implementation

[BioTurboNick]

As documented in #43933 , a user may run into an unexpected array if they attempt to concatenate arrays using the multidimensional syntax but don't know the semicolon precedence rules:

[[1 1]; 2 ;; 3 ; [3 4]]
[[1 ;;; 1]; 2 ;;; 3 ; [3 ;;; 4]]

Naively, one might think these expressions would work, assuming ; had lowest precedence. The _typed_hvncat_dims implementation needed to do more to check the dimensions of the arguments.

Fixes #43933

Should be backported to 1.7, yes?

[BioTurboNick]

Looks like it works! Slightly slower (~3%), no new allocations. Would be nice not to have to iterate over the arguments twice, but it's a small cost.