Fixing more nnkBracketExpr not being checked in hasCustomPragma calling getImpl of nnkBracketExpr

[Clonkk]

@Araq This is a follow-up of #19427

It's mostly the same issue : getImpl being called on nnkBracketExpr without checking. I can only fix it where I encounter it (necessary to fix moigagoo/norm#132). but there may other.

I'm wondering if a better fix wouldn't be to check for nnkBracketExpr in a getImpl wrapper (since getImpl is magic) like :

proc getImplChecked(node: NimNode) : NimNode =
  if node.kind() == nnkBracketExpr:
    getImpl(node[0])
  else:
    getImpl(node)

but I do not know the ramification of such a change; or if it's better or worse than adding manual check whenever the issue arise.

[Clonkk]

Continuing in #19451