[MM-56713] Show consistent markdown formatting buttons & keyboard shortcuts when editing messages (#29398)

* footer

* changes

* edit

* some changes

* form submit

* ci fixes

* rev fix 1

* ci fix

* Fixed some styles

* Added delete on empty post option

* fix E2E tests

* fix more tests

* Fixed UI isses when editing post in RHS

* Fixed formatting bar behjaviour

* Reset draft to original post when cancelling or escaping

* DFisplayed @mention warning

* fixed existing test

* Added test for @mention during editing

* Displayed long message warning during edit post

* Removed a console log:

* Handled message with image links when using image proxy

* Fixed a11y styling for button

* Fixed emoji picker keyboard shortcut

* Checnged edit box ID

* Added draft test

* Fixed edit text box id

* e2e fix

* e2e fix

* handled deleting empty fposts

* Fixed e2e test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Harshil Sharma <harshil.sharma@mattermost.com>
Co-authored-by: yasserfaraazkhan <attitude3cena.yf@gmail.com>

e2e-tests/cypress/tests/integration/channels/keyboard_shortcuts/dot_menu_spec.js

@@ -68,8 +68,8 @@ describe('Keyboard Shortcuts', () => {
             cy.uiPostDropdownMenuShortcut(postId, 'Edit', 'E');
 
             // # add test to the message
-            cy.get('body').type(postEditMessage);
-            cy.get('body').type('{enter}');
+            cy.get('#edit_textbox').type(postEditMessage);
+            cy.get('#edit_textbox').type('{enter}');
 
             // * Verify edited message
             cy.uiWaitUntilMessagePostedIncludes(postMessage + postEditMessage);

e2e-tests/cypress/tests/integration/channels/keyboard_shortcuts/up_arrow_edit_message_rhs_spec.js

@@ -26,7 +26,7 @@ describe('Keyboard Shortcuts', () => {
             cy.clickPostDotMenu(postId);
             cy.findByText('Reply').click();
             const replyMessage = 'Well, hello there.';
-            cy.uiGetReplyTextBox().type(replyMessage);
+            cy.uiGetReplyTextBox().type(replyMessage, {delay: 100});
             cy.uiGetReplyTextBox().type('{enter}');
             cy.uiWaitUntilMessagePostedIncludes(replyMessage);