[RDY] Replaced `add_spawn` with `place_spawn`

[ZhilkinSerg]

Fixes #3951.

What was changed:

• all add_spawn function calls were replaced with place_spawn function calls;
• several monster groups were added to monstergroup.json;
• some magic numbers were replaced with SEEX/SEEY defines;
• some inappropriate usages of SEEX were replaced with SEEY.

[BevapDin]

The chance of those spawns is still hard coded, shouldn't that be part of the monster group?

And I think you changed the location of the spawn slight: previously it was in the middle (at 12,12) of the 24x24 map that is used for mapgen. Now it's somewhere in the upper left 12x12 area. But this is probably not important as the monsters will move around anyway.

[ZhilkinSerg]

The chance of those spawns is still hard coded, shouldn't that be part of the monster group?

Hmm, I guess it could be changed to: m->place_spawns( mongroup_id( "GROUP_JABBERWOCK_ONLY" ), 1000, 0, 0, SEEX, SEEY, 1 );

Most of this will eventually moved from cpp to json.

And I think you changed the location of the spawn slight: previously it was in the middle (at 12,12) of the 24x24 map that is used for mapgen. Now it's somewhere in the upper left 12x12 area. But this is probably not important as the monsters will move around anyway.

Yes, it should probably be changed to 0, 0, SEEX * 2 - 1, SEEY * 2 -1.

Will address that in separate PR.