partially fix: rjsf-team#3072 by adding generic type support to the mui theme
- In `@rjsf/core` added a few missing generics to utility function calls in `CheckboxWidget`, `ObjectFieldTemplate`, `SubmitButton` and `SelectWidget`
- In `@rjsf/mui` added generic type support as follows:
  - Updated all of the template and widget components to add the `T = any`, `S extends StrictRJSFSchema = RJSFSchema` and `F extends FormContextType = any` generics on the function definitions, types and utility function calls
  - Added a `generateForm<T, S, F>()` function to `MuiForm.tsx`, exporting it and exporting the default `MuiForm` as a call to `generateForm()`
  - Added a `generateTemplates<T, S, F>()` function to the `Templates.tsx`, exporting it and exporting the default `Templates` as a call to `generateTemplates()`
  - Added a `generateTheme<T, S, F>()` function to the `Theme.tsx`, exporting it and exporting the default `Theme` as a call to `generateTheme()`
  - Added a `generateWidgets<T, S, F>()` function to the `Widgets.tsx`, exporting it and exporting the default `Widgets` as a call to `generateWidgets()`
  - Updated the main `index.ts` for the theme to also export the `generateXXX()` functions
- Fixed the number of new packages listes in the upgrade guide from 3 to 4
- Updated the `CHANGELOG.md` accordingly