Move `Grid` instance from `Data` into `CoreComponents`

**Is your feature request related to a problem? Please describe.**
It's a much more natural home for `Grid`, and can then be added cleanly to all models via the `BaseModel`. Passing `CoreComponents` and possibly `Config` to `Data` is then likely part of the plan for fixing old problems like #208.

**Describe the solution you'd like**
Add `Grid` to `CoreComponents` and populate `BaseModel.grid` as a core shared attribute, rather than it being oddly accessed through `Data`.

Start by tracing how Grid is currently stored and accessed through Data, then inspect CoreComponents and BaseModel to understand their shared attributes. Done means Grid is added to CoreComponents, BaseModel.grid is populated as a core shared attribute, and access through Data is no longer required.

Written by the indexing model from the issue text.