entt/TODO

EXAMPLES
* filter on runtime values/variables (not only types)
* support to polymorphic types (see #859)

DOC:
* custom storage/view
* update entity doc when the storage based model is in place
* in-place O(1) release/destroy for non-orphaned entities, out-of-sync model
* view: single vs multi type views are no longer a thing actually
* bump entities, reserved bits on identifiers

TODO:
* deprecate non-owning groups in favor of owning views and view packs, introduce lazy owning views
* bring nested groups back in place (see bd34e7f)
* work stealing job system (see #100) + mt scheduler based on const awareness for types
* view: reduce inst due to/improve perf with index-based approach in dispatch_get/pick_and_each/each (single type too, define storage ::at and ::at_as_tuple)
* view: update natvis as needed after the last rework, merge pools/filter in the same array, drop check (?) and turn view into a position
* view: type-only view_iterator (dyn get/excl sizes), type-only basic_common_view (dyn get/excl sizes with pointer to array from derived)
* combine version-mask-vs-version-bits tricks with reserved bits to allow things like enabling/disabling
* self contained entity traits to avoid explicit specializations (ie enum constants)
* auto type info data from types if present
* test: push sharing types further
* after non-continuous generation for entity storage:
  - get/reset placeholder to position after saving/loading (avoid long lookup)
  - allow skipping/reserving entity identifiers
  - documentation for reserved entities
* storage entity: no emplace/insert, rename and add a fast range-push from above
* view: propagate tombstone check request to iterator
* table: pop back to support swap and pop, single column access, empty type optimization
* checkout tools workflow
* improve front (no multiple checks) and back (ie no contains) for multi-type view
* cleanup common view from tricks to handle single swap-only and in-place, if constexpr branches
* entity based component_traits
* review cmake warning about FetchContent_Populate (need .28 and EXCLUDE_FROM_ALL for FetchContent)
* after removing meta prop vectors, copy meta objects in their handles directly
* suppress -Wself-move on CI with g++13
* view and view iterator specializations for multi, single and filtered elements
* organizer support to groups
* meta range: move id to meta objects and return plain types (?), then remove id from meta base and meta ctor too
* refine the storage fallback mechanism for views (ie alloc?)
* sigh_mixin: automatic signal registration
* sigh_mixin: change cb signature from reg/entt to storage/entt (breaking for the good)
* don't pass reactive storage by default to callback
* runtime types support for meta for types that aren't backed by C++ types
* bypass vtable in any (improvements available for move/get, add more policy types)