Add the rest of the new Demo feature to PSDK

MR Description

• This MR adds 6 features/corrections/etc.:
  • Add new features to the animate_from_charset method
  • Add a no_slide attribute to Game_Character (to make so that a Game_Character/Event/Player is totally unaffected by any sliding)
  • Add a height_changer attribute to Sprite_Character to modify the y rect of a Sprite_Character (helps in simulating disappearances of partial disappearance for certain things like platforms)
  • Migrate the shops ID data to db_symbol and ensure all future data will use db_symbols
  • Add the possibility to disable the looping of a Gif displayed as a RMXP Picture (and know if it's done or not)
  • Add some sort_z calls to some Battle transitions

Tests to realize

Animate_from_charset

Create a charset_animation using the animate_from_charset method:

• with the "repeat: 3" parameter: the animation should be played 3 times only and then stop
• with the "last_frame_delay: true" parameter: the animation should add a small delay between the moment the last frame is displayed and the real end of the animation (can be verified by putting a wait_charset_animation after the animate_from_charset)
• with the "reset_at_end: true" parameter: the animation should return to the very first frame at the end of the animation

No slide

• Add the name tag [noslide=on] to the name of an event: this event shouldn't be affected by Ice or mudslides anymore
• Type $game_player.no_slide = true in the console: the player shouldn't be affected by Ice or mudslides anymore

Sprite_Character height changer

• Type $game_player.height_changer = 8 in the console: part of the player's sprite should be erased.

Shop migration

• Just test some shops, should work with no problem

Gif looping

• In an event, add this script command $scene.spriteset.sprite_picture(2).gif_loop_disabled = true, then assign a gif to the Picture n°2: the gif should play one time only, then stop.

sort_z in transitions

• Launch a battle using transition 2 and 3: both should be correctly displayed and the message box should be properly displayed too.