[MM-61592]: Updated the Theme list section in the settings modal (#29596)

* [MA-13]: Updated the Theme list section in the settings modal

* [MA-13]: Fixed failing e2e test cases

* [MA-13]: Fixed accordion and removed aria-label from button

* [MA-13]: Fixed grouping of radio buttons

* [MA-13]: Updated the Theme list structure

* [MA-13]: Minor styling changes

---------

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

e2e-tests/cypress/tests/integration/channels/settings/display/theme/code_theme_colors_spec.js

@@ -35,10 +35,10 @@ describe('Settings > Display > Theme > Custom Theme Colors', () => {
             cy.get('#customThemes').check().should('be.checked');
 
             // # Open Center Channel Styles section
-            cy.get('#centerChannelStyles').click({force: true}).wait(TIMEOUTS.ONE_HUNDRED_MILLIS);
+            cy.get('#centerChannelStylesAccordion').click({force: true}).wait(TIMEOUTS.ONE_HUNDRED_MILLIS);
 
             // # Select custom code theme
-            cy.get('#codeThemeSelect').should('be.visible').scrollIntoView().select(theme.name);
+            cy.get('#codeThemeSelect').scrollIntoView().should('be.visible').select(theme.name);
 
             // * Verify that the setting changes in the background?
             verifyLastPostStyle(theme);