[th/nm-ptr-array] add and use NMPtrArray

NMPtrArray was introduced while working on a fix for https://bugzilla.redhat.com/show_bug.cgi?id=2060684, but it ended up being independent.

It was also previously on review on !1469 (closed). !1469 (closed) got closed and is deprecated by this (and other merge requests).

Here again.

What Beniamino said:

• !1469 (comment 1673055)
• !1469 (comment 1697345)

is still relevant on this MR.