Add scripts to make a pruned “StoryQuest Kit” bundle

[wjt]

Rather than having Core: Threadbare participants start from a fork of
the entire repo, we want to try giving participants a stripped-down copy
of the project - specifically with all LoreQuests and other StoryQuests
removed. The goals are manifold:

• Reduce the cognitive burden of navigating a large project.

• Reduce the need to take special steps to deep link to a StoryQuest for
  testing: the team's StoryQuest should be launched from the title
  screen.

• Reduce the number and size of the files in the project, saving
  electrons and helping with performance in Backstitch.

• Move us towards a model where rather than expecting that all
  storyquests will be merged upstream (requiring learners to take
  special care to only modify files in their folder, increasing
  complexity; and hitting human scalability cliffs in the form of there
  only being two full-time maintainers of the game reviewing StoryQuest
  submissions) we instead treat them more as stand-alone games. For the
  ones we choose to merge upstream, we can do the necessary work to
  confine them to their own folder at that point; and you could imagine
  adding a way to launch a separately-downloaded .pck for a StoryQuest.

As well as removing the lore_quests and story_quests folders, we also
have to remove the world_map folder (i.e. Fray's End and connected
scenes) because these scenes now link directly to LoreQuests.

I also decided to remove the non-CC0 Tiny Swords free pack, which we
have special permission to redistribute but which is not used outside of
one StoryQuest. This significantly reduces the number of files in the
project, which is helpful for Backstitch.

Having removed these files, we adjust the project settings so that the
quest launched from the title screen is the NO_EDIT template, and the
scene to return to when a quest is completed or abandoned is the title
screen. When we have Dev Island/Archipelago, we will change the latter
to that.

One approach would be to have learners modify the NO_EDIT template
in-place, in which case we would want to rename all those files and
delete the bootstrap tool. For now I just updated the StoryQuest
bootstrap tool to change the initial quest to the newly-duplicated one.

I checked for references into these folders from elsewhere in the game
as follows:

git grep -E \
    '(lore_quests|story_quests|world_map|tiny-swords-non-cc0)' \
    ':!scenes/quests/lore_quests' \
    ':!scenes/quests/story_quests' \
    ':!scenes/world_map' \
    ':!assets/third_party/tiny-swords-non-cc0'

In a perfect world there would be no output from this command. There are
some lingering references: for example, the elders' dialogue references
the paths to various quest.tres resources. However there are (as far
as I can tell) no references that will cause a scene or resource to fail
to load. (This command is imperfect because, for example, teleporters
refer to other scenes by their UID stored as a string.)

Creating the bundle is implemented with two scripts:

1. A GDScript script which deletes files and adjusts project settings,
   which is most easily done using Godot's own APIs (and reuses some
   preexisting logic).
2. A shell script which drives the GDScript script, then does some
   additional stuff (downloading the backstitch launcher, running Git
   commands) which is more easily accomplished in shell.

I couldn't resist calling the script StoryQuest Construction Kit
Construction Kit (SQCKCK for short) but this is a placeholder name!

Still to do: a GitHub Actions workflow to run this.

Helps #2563

[wjt]

@jgbourque Still a work in progress but please have a read of the description above then take a look at https://drive.google.com/file/d/1-6nJkNDaWB57XZlTyY2YZhawQKTvSNQ_/view?usp=sharing

[github-actions]

Play this branch at https://play.threadbare.game/branches/endlessm/wjt/sqckck/.

(This launches the game from the start, not directly at the change(s) in this pull request.)

[wjt]

The point of committing the pruned build to Git is:

1. If we keep that commit somewhere, then if we do want to import a quest built from this kit into the upstream repo, it will be much easier to diff!
2. I want to keep open the option of using Git to make a StoryQuest. What I have in mind is that our magic repo-forking script would not base the new repo off the upstream main branch but off a branch containing the latest storyquest kit. This new repo would be detached from endlessm/threadbare (implementation TBD) so would operate as its own separate universe.