Compiler permits override on postinit() and init(), but probably shouldn't

[bradcray]

In #26430 (review), @cassella convincingly pointed out that override on a proc postinit() call doesn't really make sense, as the postinit() calls aren't really called in a dynamically dispatched way. Assuming neither of us are missing anything, this suggests that the language shouldn't really permit override to be attached to postinit() calls. Checking, it seems we also permit override to be attached to init() calls, but this also doesn't seem quite right. Note that the override calls don't seem to have an effect on the program behavior (which is somewhat reassuring).

Associated Future Test(s):

• test/classes/initializers/inheritance/override.chpl Add futures showing that override can be applied to init() and postinit() #26518
• test/classes/initializers/postInit/override.chpl Add futures showing that override can be applied to init() and postinit() #26518
• test/classes/initializers/postInit/override2.chpl Add futures showing that override can be applied to init() and postinit() #26518
• test/classes/initializers/postInit/override3.chpl Add futures showing that override can be applied to init() and postinit() #26518

[bradcray]

@DanilaFe : This follows up on your questions from today's demo.