v8 - post launch refinement

[AnaBelgun]

Following v8 launch, based on users' feedback and discussions, refine the remaining tasks and re-prioritise:
Miscellaneous:

• AsyncLoader: check if load is being called from a computed and if so, throw an error #5324
• Model architecture: Add error boundaries in the React UI #3487
• Show error message if Cesium Ion access token is invalid #4739
• How to handle broken/unsupported catalog items - UX #5188
• Clearly communicate which APIs and public and which ones are private #5466
• Update model layer docs with more strict rules around mobx.action and async/Promise functions #5033
• Using createStratumInstance with traits which have nested objectTraits #4727
• Local storage migration #4206
• Migration v7 - v8 - Dynamic groups #5640

Model layers:

• Add point and polyline support for mapbox vector tile items using a library #3846
• TerriaJS v7-v8: TerriaJsonCatalogFunction support  #5601
• Consistent usage of LoadableStratum #5465
• Find and remove duplicate traits #5464
• Mixins are applied more than once #5398
• Consolidate naming for Mixin instance type #5374
• Model architecture: Enable eslint for .ts files #3303
• Basemap images for default basemaps should be moved back to terriajs #5383
• All Catalog items should use GeojsonMixin instead of creating GeoJsonCatalogItems #5380
• Implement TileErrorHandlerMixin for all tile-based CatalogMembers #5154
• Inserting vs updating models from share data (or initSources) #5023
• Catalog item composition vs Mixins #4705
• Model architecture: Allow traits in strata to be null #3375
• V7 - V8: Implement Ideal Zoom for SOS catalog item #5047