feat: record every core a rom folder offers

The rom folders files kept the default core of each folder only, so a
core the user picks in the frontend's menu was not known to read its
sets there. Each folder now lists its offers: every <core> of every
<emulator> in AmberELEC's es_systems.cfg (arcade:
packages/ui/emulationstation/config/es_systems.cfg:116-150), every core
of EmuELEC's es_systems.json, every add_emu_core of ROCKNIX's emulators
package.mk with the device case it is written under (arcade: 218-229),
and the emulator of every ES-DE <command>. A core written under every
branch of a case is offered unconditionally. The ES-XML, ES-JSON,
ELEC-conf and ES-DE setups are rescraped at their pins: archr, arkos,
chaos, darkos, jelos, kolos, pan4elec, retrobat and unofficialos gain
the same records and nothing else.

A libretro core offered for a folder reads the sets it loads beside the
game there, as the default one does.

Manifests, roms folders gaining sets read beside the game:
- AmberELEC: +215 (293.1 MB) in fbneo, arcade and mame, for MAME 2010,
  2015, 2016 and 2003-Plus. 1 omission leaves.
- EmuELEC: +291 (232.0 MB) in cps1, cps2, cps3, mame, fbneo and
  arcade, for MAME 2010 and 2003-Plus. 47 omissions leave.
- ROCKNIX: +501 (538.7 MB) in fbneo, neogeo, cps1, cps2, cps3, arcade
  and mame, for MAME 2010, 2015 and 2003-Plus. 120 omissions leave.
- EmuDeck: +306 (251.2 MB) in cps, cps1, cps2, cps3, arcade and mame,
  for MAME 2000, 2003, 2003-Plus and 2010. 92 omissions leave.
Each omission that leaves was a set named as read outside the BIOS
folder. RetroDECK and the other platforms do not change. No file
leaves, and verify --all keeps its severity and status counts.

scripts/common.py

@@ -3419,10 +3419,11 @@ def content_folder_tags(config: dict) -> set[str]:
     A core reading its BIOS sets beside the game (MAME 2003's osd_get_path
     gives FILETYPE_ROM the content directory) reads them in the folder of
     the system it is launched for. The folders come from the platform's own
-    lists: ``libretro_systems``, the default core of each folder its rom
-    folders file records, the cores a system offers under its own name, and
-    the systems a RetroPie package registers. A platform with no roms root,
-    or one keeping no folder per system (RetroArch, Lakka), gives none.
+    lists: ``libretro_systems``, every core a folder of its rom folders file
+    offers (its default, its board defaults, ``offers``), the cores a system
+    offers under its own name, and the systems a RetroPie package registers.
+    A platform with no roms root, or one keeping no folder per system
+    (RetroArch, Lakka), gives none.
     """
     if config.get("inherits_from") == "emulatorjs":
         # EmulatorJS writes the BIOS a frontend hands it and the game to
@@ -3438,7 +3439,8 @@ def content_folder_tags(config: dict) -> set[str]:
     for core, systems in (config.get("libretro_systems") or {}).items():
         pairs |= {(_core_key(core), str(s)) for s in systems or []}
     for row in rows:
-        for choice in [row, *(row.get("board_defaults") or {}).values()]:
+        choices = [row, *(row.get("board_defaults") or {}).values(), *(row.get("offers") or [])]
+        for choice in choices:
             if choice.get("core") and choice.get("emulator") in LIBRETRO_RUNNERS:
                 pairs.add((_core_key(choice["core"]), str(row["folder"])))
     for system in (config.get("systems") or {}).values():