Block Editor: Improve the way terms are matched in the block inserter

[gziolo]

Description

This is preliminary work for integration block patterns with the inserter. While contemplating how this could be achieved, I did some refactoring to make the process easier for myself and future contributors by moving related code to search for blocks to its own file. It quickly led to a few discoveries:

• categories were fetched directly from the store, which might lead to some sync issues when categories get updated, added or removed by 3rd party plugins
• the search mechanism was very basic and it would be hard to find a good heuristics to include block patterns there

What this PR covers:

• InserterMenu get categories injected using withSelect HOC
• search logic was refactored to:
  • ignore whitespaces between words
  • ignore everything which doesn't resemble a word
  • match terms by scanning all possible properties used at the same time (block title, category name, and keywords) - all of them need to be matched in any combination

Before

After

How has this been tested?

Unit tests were updated, new cases were covered:
npm run test-unit

UI part can be tested either with Storybook and the playground or directly in the block editor in WordPress. Storybook is just easier to develop with :)

Types of changes

Enhancement + refactoring

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR. .

[mapk]

Wow, such a great improvement here! Thanks for creating this PR, @gziolo.