Introduce `GenTreeDebugOperKind` (#64498)

Introduce `GenTreeDebugOperKind` (#64498)

* Introducing GenTreeDebugOperKind

To track invariants related to opers in asserts
without increasing the size of the primary oper
kind table.

Some shuffling of the oper table to make it look better.

* More "gtlist.h" cleanup

Put all OperIsIdir opers together, fix up formatting,
move opers around to more logical places.

* Remove redundant asserts

* GTK_NOTLIR -> DBK_NOTLIR

There is not a lot of point in this being a "release"
oper kind, as it is really only useful for debug checks.

* GTK_NOCONTAIN -> DBK_NOCONTAIN

* Fix formatting...