Name as an object not supported for body_part type

[snipercup]

Describe the bug

Writing the body_part name as "name": { "str": "right arm", "str_pl": "arms" },
produces this error:
DEBUG : Error: data/mods//dda/../../json/body_parts.json: line 71:13: Expected string

"id": "arm_l",
"type": "body_part",
"name": {
        ^
          "str": "left arm", "str_pl": "arms" },
"heading_singular": "L. Arm",
"heading_plural": "Arms",

FUNCTION : bool main_menu::load_character_tab(bool)
FILE : src/main_menu.cpp
LINE : 1069

Steps To Reproduce

Steps to reproduce the behavior:

1. Write "name": { "str": "right arm", "str_pl": "arms" }, in a body_part
2. Remove name_plural property
3. Start a game
4. Observe error

Expected behavior

Accepting the name as an object

Versions and configuration

• OS: Windows
  • OS Version: MINGW/CYGWIN/MSYS2 on unknown Windows version
• Game Version: 0.D-11806-g9df6c1607d [64-bit]
• Graphics Version: Tiles
• Mods loaded: [
  Dark Days Ahead [dda],
  Disable NPC Needs [no_npc_food],
  Aftershock [aftershock],
  C.R.I.T Expansion Mod [crt_expansion],
  Magiclysm [magiclysm],
  Bens GF recipes [Tolerate_This],
  Craftable Gun Pack [craftgp],
  DeadLeaves' Fictional Guns [FIC_Weapons],
  Garden Pots [growable-pots],
  Icecoon's Arsenal [ew_pack],
  Makeshift Items Mod [makeshift],
  Medieval and Historic Classes and Shields [Medieval_Stuff],
  More Survival Tools [More_Survival_Tools],
  Mythological Replicas [nw_pack],
  DinoMod [DinoMod],
  Modular Turrets [modular_turrets],
  Salvaged Robots [Salvaged_Robots],
  Mutant NPCs [mutant_npcs],
  More Locations [more_locations],
  Fuji's More Buildings [FujiStruct],
  Urban Development [Urban_Development],
  Folding Parts pack [deoxymod],
  Vehicle Additions Pack [blazemod],
  Tanks and Other Vehicles [Tanks],
  Roadheader and other mining vehicles [Heavy miners],
  Necromancy [necromancy]
  ]

Additional context

In order to implement #36611 and #37698 and fix #36110 this issue needs to be solved.

[snipercup]

To quote Qrox:

This wasn't changed to the new format, because it doesn't actually use the new format: "name_plural" here means the name for a pair of body parts, and was only named "name_plural" because it was (incorrectly) implemented as a plural name. If this is to be changed, the proper change would be renaming it from "name_plural" to something like "name_pair".