chore: migrate to gestalt v7—fork 🅰, keep subsystems separate

[keturn]

This is a variant of #4593. It diverges after 20546f1 in an attempt to find an alternative to moving subsystems back in to the org.terasology.engine namespace.

The diff is usable if you only include the later commits, i.e. after all the import changes. https://github.com/MovingBlocks/Terasology/pull/4622/files/94e1e419d3d9cff599a2ec4e7bd68cdf4983ebc3..HEAD
but this trick is working less well the longer this branch is around, as that diff includes merge commits in a way that diffs from the branch root do not.

To generate a diff from the command line that excludes the import clutter:

git diff --ignore-matching-lines="^import .*"  --ignore-all-space \
    origin/develop origin/feature/migrate-gestalt-v7.a 

Build Instructions

Use chore/gestalt-v7-migration branches for /modules/*.

Notes for Reviewers

• The place most related to gestalt-module is the ModuleManager: https://github.com/MovingBlocks/Terasology/blob/feature/migrate-gestalt-v7.a/engine/src/main/java/org/terasology/engine/core/module/ModuleManager.java
  but there are also changes spread across asset loaders and type handlers.
• Does anyone think it is critical that we keep building reflections.cache at compile time? In play testing, do you notice this being a lot slower to start or join a game?
• Do we need to fix anything about the way we're handling NUI or subsystems? These are libraries that are outside of engine, but define things that need to be discoverable to the ECS or TypeRegistry systems. i.e. they have @API annotations or have classes involved in some getSubtypes query.
  • is feature: migrate to gestaltv7 #4593's approach better?

Notes for Testing

To Do

• reinstate cache-reflections build tasks?
• Merge gestalt fix for asset manager race condition: fix(AutoReloadAssetTypeManager): synchronize methods to avoid NPE gestalt#102
• something jmh-related preventing running from IntelliJ?
• tidy use of google() repository
• migrate the modules: many have branches under the name chore/gestalt-v7-migration

[keturn]

This isn't to the point where it does anything interesting, but it has some gradle chores I wanted to make sure were pushed somewhere.

[keturn]

if you need to check out things before this was merged, see tag https://github.com/MovingBlocks/Terasology/tree/pre-gestalt-v7-merge