Collections of blocks regsitered via `registerBlockCollection` now
appear at the end of the block inserter enabling additional organization
of blocks.

The `BlockTypesList` now expects `sections` to support the `SectionList`
used within it for displaying block collections. Prior to this change,
an error was thrown.

The `BlockTypesTab` now relies upon additional store selectors. The lack
of mocks for these selectors caused test failures.

The code contained redundant selectors against the store for the block
type list. This change refactors the native inserter to match the web
counterpart, utilizing the selector leveraged by the web.

While verbose, passing explicit props is likely more orthodox and
straightforward to interpret.

The key for this component's sections is now `key`, not `id`, which
resulted in undefined key values returned here. However, the default
`keyExtractor` already searches for `key` and then `id`, so this can be
safely removed.

The block created from within this callback appears to be in a format
that is incompatible with the native editor at this time. Specifically,
this appeared to break Embed block variants, e.g. Vimeo. A future
improvement would be to investigate this further in hopes of aligning
web and native.

Improve legibility of section headers whenever blocks scroll beneath the
header.

Leverage merely an icon with text made dark mode support more
challenging. Rendering text allows for easy swapping of color schemes.