Add CSS cascade layers for Compound, shared components, and app/web styles (#33302)

* Layer Compound and shared component CSS

* Layer app theme CSS

* Remove !important flags from ActionBarView

* Remove unnecessary !important statements from shared components

* Avoid dead code errors for *.pcss just because layer is specified after @import url

* Remove unnecessary !important styling

* Override Banner defaults in RoomStatusBarView

* Updated snaps

* Updated snaps

* Fix styling of media body in app/web

* Fix styling for Compound anchors

* Fix styling issues in app/web

* More styling fixes

* Fix a problem extracting css for HTMLExport

* Revert changes

* Fix for theme styling

* Add test to improve coverage

* Prettier

* Fix styling issues

* Add data-kind attribute to avoid global styling override

* Update screenshot that now is correct

* Revert data-kind attribute

* Handle LinkPreview styling in .pcss

* Fix flaky test: Avoid racing the lazy-loaded ManageEventIndexDialog

* Take care of review comments

* Updated snaps

* Updated snaps again after merge

* Remove !important from RoomStatusBar

apps/web/res/css/views/settings/tabs/_SettingsSection.pcss

@@ -12,7 +12,8 @@ Please see LICENSE files in the repository root for full details.
 
     color: $primary-content;
 
-    a {
+    /* Compound links carry data-kind and provide their own colour. */
+    a:not([data-kind]) {
         color: $links;
     }
 

apps/web/res/css/views/settings/tabs/_SettingsTab.pcss

@@ -10,7 +10,8 @@ Please see LICENSE files in the repository root for full details.
 
     color: $primary-content;
 
-    a {
+    /* Compound links carry data-kind and provide their own colour. */
+    a:not([data-kind]) {
         color: $links;
     }