net: lwm2m: Restructure LwM2M Kconfig menu

* Create submenu for protocol versions.
  Like LwM2M 1.0 vs 1.1. Object versions.
* Create submenu for engine features.
  Containing all engine tweaks that are not directly from
  protocol specification.
* Create submenu for all memory tuning options.
  For example maximum number of certain objects, buffer
  sizes, etc.
* Order all objects by object ID and show the ID in
  title.
* When multiple options depend on same feature, group
  them under if <option> ... endif. Preferably directly
  after the selection itself.
* Move IPSO and uCIFI menuentries one sublevel up.
* Drop deprecated entries to bottom.

No functional changes, just clean up of Kconfig menu.

Signed-off-by: Seppo Takalo <seppo.takalo@nordicsemi.no>