Reinstate #1007 equality of array types

[bcardosolopes]

Originally posted by @bcardosolopes in #1166 (comment)

[bcardosolopes]

cc @ChuanqiXu9

[ChuanqiXu9]

Some detailed description:

In #1166, we disabled to check for the equality of array element types for the following issue:

In an array of unions (or types containing unions), we may construct an array attribute from the initializers. However, the type of the initializers may be different for unions. #1007 is another try to solve the problem but it shows it is not easy to fix it fundamentally without introducing two type systems: one for code gen for CIR and one for lowering CIR. See the comments in #1160 (comment) for detailed analysis.