[RNMobile] refine Block borders

[jbinda]

Description

PR goal is to apply InnerBlock bordering style to other blocks on the RootList level ( full solid border ) as well as show FloatingToolbar when selected.

At this moment two commits is the minimum code change to achieve expected results. I will also do the code cleanup to remove unnecessary code in future commits.

Please also refer to:
Related gutenberg-mobile PR
Discussion on design

How has this been tested?

1. Start with below code in initial-html

/**
 * @format
 * @flow
 */

export default `
<!-- wp:group -->
<div class="wp-block-group"><div class="wp-block-group__inner-container"><!-- wp:heading -->
<h2>Group</h2>
<!-- /wp:heading -->

<!-- wp:image -->
<figure class="wp-block-image"><img alt=""/></figure>
<!-- /wp:image --></div></div>
<!-- /wp:group -->

<!-- wp:image -->
<figure class="wp-block-image"><img alt=""/></figure>
<!-- /wp:image -->

<!-- wp:image -->
<figure class="wp-block-image"><img alt=""/></figure>
<!-- /wp:image -->

<!-- wp:image -->
<figure class="wp-block-image"><img alt=""/></figure>
<!-- /wp:image -->

<!-- wp:image -->
<figure class="wp-block-image"><img alt=""/></figure>
<!-- /wp:image -->

<!-- wp:image -->
<figure class="wp-block-image"><img alt=""/></figure>
<!-- /wp:image -->

<!-- wp:image -->
<figure class="wp-block-image"><img alt=""/></figure>
<!-- /wp:image -->


`;

2. Try to play with selection on RootList block and the Group block
3. Add as many Blocks as you want to RootList to test how the modified border looks like

Screenshots

Types of changes

New feature ( apply same bordering style as in InnerBlock to RootList blocks )

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.

[koke]

Looking good. Yay for less code 😁

[pinarol]

so happy to see some complex logic removed! 🥳