hook_theme_suggestions_alter needs to statically cache results of visible blocks

Problem/Motivation

zurb_foundation_theme_suggestions_alter checks the visible blocks. However, the data is not statically cached. It causes a huge performance hit.

function zurb_foundation_theme_suggestions_alter(&$suggestions, $variables, $hook) {
  if ($hook == 'menu' || $hook == 'block') {
    // For menu blocks, check to see if the menu block is placed in an off-canvas
    // region, and if so use our custom template.
    $all_blocks = \Drupal::service('block.repository')->getVisibleBlocksPerRegion();

It ends up calling getVisibleBlocksPerRegion 41 times. And that method does not statically cache results. We could fix core, but easier here!

Here is a timeline view, each of the green blocks in that row is a call to fetch the visible blocks.

Proposed resolution

Statically cache the visible block results to reduce the number of times all blocks are loaded.