Computed field definitions created by inheritance have no provider set

Problem/Motivation

The computed field definitions created by field_inheritance_entity_bundle_field_info_alter() do not set a provider (module). If these fields are then used in a Search API index, it causes the search index config to be exported with a dependency on a null module, which in turn causes the following error when the config is imported:

Configuration search_api.index.my_index depends on the "" module that will not be installed after import.

Steps to reproduce

1. Install the Search API module and configure a search server.
2. Install Field Inheritance and (for sake of ease of testing) the Recurring Events module.
3. Add a custom field to default eventseries bundle.
4. Set up a field inheritance to inherit the custom field onto the default eventinstance bundle using the 'inherit' strategy.
5. Create a search index for eventinstance entities.
6. Add the inherited field to the index.
7. Export the config.

Expected results: The exported search_api.index.my_index.yml should contain values similar to the following:

dependencies:
  config:
    - search_api.server.elasticsearch
  module:
    - recurring_events
    - field_inheritance
    - search_api

and

field_settings:
  my_inherited_field:
    ...
    dependencies:
      module:
        - field_inheritance

Actual results: The config declares dependencies on a null module, like so:

dependencies:
  config:
    - search_api.server.elasticsearch
  module:
    - recurring_events
    - ''
    - search_api

and

field_settings:
  my_inherited_field:
    ...
    dependencies:
      module:
        - null

Proposed resolution

On the $fields[$field->idWithoutTypeAndBundle()] = FieldStorageDefinition::create($type) statement chain, call ->setProvider('field_inheritance').