Move Flex & Box component into shared component folder (#30357)

* refactor: move Flex component in shared components

* refactor: update imports

* refactor: remove Flex pcss file

* fix: Flex component css override

* test: update snapshots

* fix: html export

* chore: add css module support to jest

* chore: keep old copyright

* refactor: change `mx_Flex` in `ErrorView` to `mx_ErrorView_flexContainer`

* test: update snapshots

* refactor: move Box component in shared components

* refactor: update import and css override

* test: update snapshots

res/css/structures/ErrorView.pcss

@@ -50,7 +50,7 @@ Please see LICENSE files in the repository root for full details.
         color: var(--cpd-color-text-secondary);
     }
 
-    .mx_Flex {
+    .mx_ErrorView_flexContainer {
         margin: 0 auto;
         max-width: max-content;
         flex-wrap: wrap;