Types: Fix #1290: Rationalize and correct "mixed" style array dimensioning.

There a couple functional problems, which when reduced down also led to
some good simplifications and rationalization.  So, this commit:
 - corrects "mixed" functionality: int[A] f[B] -> f[B][A]
 - correct multi-identifier decls: int[A] f[B], g[C] -> f and g are independently sized.
 - increases symmetry between different places in the code that do this
 - makes fewer ways to do the same thing; several methods are just gone now
 - makes more clear when something is copied or shared

gtests/AST.FromFile.cpp

@@ -199,6 +199,7 @@ INSTANTIATE_TEST_CASE_P(
         "loopsArtificial.frag",
         "matrix.frag",
         "matrix2.frag",
+        "mixedArrayDecls.frag",
         "newTexture.frag",
         "Operations.frag",
         "overlongLiteral.frag",