What?

This PR enables developers to completely extend the Query Loop block options, deciding which settings should be available and which should not.

Why?

Developers might want to create Query Loop block variations which are more specific to their environment, and, as such, don't require all of the settings available by default on the Query Loop block. Even further, some of these settings might break block variations.

How?

This PR proposes a way to enable this customization that is completely backwards compatible, and enables a simple API for developers to hook into and extend the settings.

1. A new attribute called disabledInspectorControls has been added to the block. Developers can pass an array of strings corresponding to the keys of the settings that they want to disable to not render them on the inspector sidebar. Since we are not using TypeScript, perhaps adding a clear JSDoc documentation of the keys available by default could be helpful. However, no harm is done if wrong strings are passed, and the block behaves normally when the attribute is an empty array or undefined, preserving backwards compatibility.
2. disabledInspectorControls also accept a list of strings corresponding to the collapsed filters. However, since filters have been moved to a ToolsPanel, in order to allow developers to extend that panel and completely integrate new optional filters to the inspector, a new WordPress filter has been added (provisional name: editor.QueryLoop.FilterControls, naming convention inspired by filters found in components/Autocomplete).
3. Taking advantage of these changes, all the controls have been refactored out of the inspector-control/index.js file into their own file, cutting the size of that file by more than half and making it more readable. Now, it is much clearer what each component is responsible for, and what properties are required, instead of having all the logic mixed into one component.

Note
In the interest of keeping my edits as minimal as possible, I preserved the already existing default exports for editor components which had been refactored, and added named exports below them.

Basically, the default exports have no knowledge of the context in which they are rendered, which might be a good thing. However, considering they are unlikely to be used in different context, they could arguably contain their rendering logic, and we could simplify the code even further. But I have no strong opinions on this, if we want to leave them as they are and enable reusability in different contexts.

@gziolo @ntsekouras I'm publishing this as a Draft PR to get your comments before I submit it for full review, in case you disagree with some of the approach taken here.

Testing Instructions

Warning
Testing instructions are WIP

1. Smoke test the default Query Loop block and verify all settings and filters still work.
2. Create a Query Loop variation (or just instantiate the block programmatically) by adding the disabledInspectorControls attribute, like so:

registerBlockVariation( 'core/query', {
  name: 'test/my-query',
  title: 'My Query',
  attributes: {
    disabledInspectorControls: [ 'InheritFromTemplate', 'PostType' ],
  },
  innerBlocks: [
    [
      'core/post-template',
      {},
      [ [ 'core/post-title' ], [ 'core/post-featured-image' ] ],
    ],
    [ 'core/query-pagination' ],
    [ 'core/query-no-results' ],
  ],
  scope: [ 'block', 'inserter' ],
} );

3. Add it to the Editor.
4. Verify that the listed settings are not available in the Inspector.
5. Add a WordPress filter to extend the Inspector Filters, like so:

const MY_FILTERS = {
  MyFilter: ( props ) => (
    <ToolsPanelItem
      hasValue={ /* ... */ }
      label={ 'My Filter' }
      onDeselect={ /* ... */ }
    >
      <TextControl
        label={ 'My Filter' }
        value={ /* ... */ }
        onChange={ /* ... */ }
      />
    </ToolsPanelItem>
  ),
};

const withMyFilters = ( filtersMap, props ) => {
  return {
    ...filtersMap,
    ...MY_FILTERS,
  }
};

addFilter(
  'editor.QueryLoop.FilterControls',
  'core/query',
  withMyFilters
);

6. Verify your filter appears on the Filters ToolsPanel dropdown.

Screenshots or screencast

Notice the missing settings on the right, and a new filter within the Filters ToolsPanel.