Mm 62677 - modal focus management - find channels modal (#29957)

* MM-62312 - modal focus management; revamp quick switch channel modal!

* get quick switch test working

* configure the generic modal to accept refs to focus within and onhide to the origin element

* apply pr feedback, get modal element get autofocus, use id instead of ref

* update more direct channels modal to use generic modal

* fix unit tests and snapshots

* fix unit tests

* fix modal margin top to fit in smaller screens

* fix e2e test

* remove unnecesary onexited extra call

* fix e2e tests

* set correct label

* fix snapshots

* create helper function for sending custom focus event

* migrate quick switch modal to use new approach to focus

* migrate more direct channels modal to new approach

* fix snapshots

* fix types

* fix modal closing behavior

* fix snapshots

* fix cypress tests

* remove only

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

e2e-tests/cypress/tests/integration/channels/messaging/focus_move_spec.js

@@ -142,7 +142,7 @@ function verifyFocusInAddChannelMemberModal() {
     cy.get('#channelLeaveChannel').should('be.visible');
 
     // # Click 'Add Members'
-    cy.get('#channelAddMembers').click();
+    cy.get('#channelInviteMembers').click();
 
     // * Assert that modal appears
     cy.get('#addUsersToChannelModal').should('be.visible');