Support E2E stress tests in run_tests.js (#29682)

* [skip ci] Adapt run_tests.js for stress testing
* [skip ci] Make channel_read_after_permalink_spec.js retry-able
* [skip ci] Fix ui_commands.ts fix
* [skip ci] Improve postMessageAndWait
* [skip ci] Fix unread_on_public_channel_spec.js
* [skip ci] Demote unread_on_public_channel_spec.js
* Update e2e-tests/README.md

Co-authored-by: Saturnino Abril <5334504+saturninoabril@users.noreply.github.com>

* [skip ci] Fix mesage_reply_bot_post_spec.js

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Saturnino Abril <5334504+saturninoabril@users.noreply.github.com>

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

@@ -18,7 +18,7 @@ describe('Messaging', () => {
     let testUser;
     let otherUser;
 
-    before(() => {
+    beforeEach(() => {
         cy.apiInitSetup().then(({team, channel, user}) => {
             testTeam = team;
             testChannel = channel;

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

@@ -144,7 +144,7 @@ describe('Messaging', () => {
                     cy.uiCloseRHS();
 
                     // * Verify that the reply is in the channel view with matching text
-                    cy.get(`#post_${replyId}`).within(() => {
+                    cy.get(`#post_${replyId}`).scrollIntoView().within(() => {
                         cy.findByTestId('post-link').should('be.visible').and('have.text', 'Commented on ' + bot.username + 'BOT\'s message: Hello message from ' + bot.username);
                         cy.get(`#postMessageText_${replyId}`).should('be.visible').and('have.text', replyMessage);
                     });