Previously we were discovering plugin outlets by checking first for dedicated template files, and then looking for classes to match them. This doesn't work for components which are entirely defined in JS (e.g. those authored with gjs, or those which are re-exports of a colocated component).
This commit refactors our detection logic to look for both class and template modules in a single pass. It also refactors things so that the modules themselves are required lazily when needd, rather than all being loaded during app boot.
The primary motivation is to simplify `eagerLoadRawTemplateModules` which curently introspects the module dependencies (the `imports` at runtime). This is no longer supported in Embroider as the AMD shims do not have any dependencies (since it's managed internally with webpack).
In the past, the result of template compilation would be stored directly in `Ember.TEMPLATES`. Following the move to more modern ember-cli-based compilation, templates are now compiled to es6 modules. To handle forward/backwards compatibility during these changes we had logic in `discourse-boot` which would extract templates from the es6 modules and store them into the legacy-style `Ember.TEMPLATES` object.
This commit removes that shim, and updates our resolver to fetch templates directly from es6 modules. This is closer to how 'vanilla' Ember handles template resolution. We still have a lot of discourse-specific logic, but now it is centralised in one location and should be easier to understand and normalize in future.
This commit should not introduce any behaviour change.
We were sharing `Discourse` both as an application object and a
namespace which complicated things for Ember CLI. This patch
moves raw templates into `__DISCOURSE_RAW_TEMPLATES` and adds
a couple helper methods to create/remove them.
