refactor: Avoid private useBlockEditorSettings API (#108)

* refactor: Avoid private useBlockEditorSettings

The `useBlockEditorSettings` function is not exported, even as a private
API. Using it is brittle, at best, and the approach is not possible when
sourcing WordPress package scripts from remote sites.

These changes still patch the `@wordpress/block-editor` package to (1)
allow the "quick inserter" to open the primary inserter and (2) enable
the Media tab in the inserter. Long-term, we should remove these patches
and replace them with changes to core.

* fix: Avoid exception from incomplete post data

When a post object is unavailable, we must ensure the raw title and
content fields have fallback values. Otherwise, the host bridge logic
throws while referencing values on an undefined object.

* fix: Enforce fixed toolbar

Now that we rely upon `EditorProvider` over `BlockEditorProvider`, we
can no longer configure the former with the `hasFixedToolbar` prop.
Instead, we must rely upon the preference store configuration.

* refactor: Remove now redundant `useGBKSettings`

We now render `EditorProvider` rather than `BlockEditorProvider`, so we
no longer configure the latter with explicit settings. We also do not
have explicit settings we need to pass to the former, so we pass an
empty object to avoid exceptions from referencing values on an undefined
object.

* task: Capture build output

Author: dcalhoun