fix(OOUI): 🐛 use fixed font size for some UI of VisualEditor and DiscussionTools

OOUI has some alignment issues when used with different font size.
This patch is a reproduction of the upstream patch applied to various extension.

Task: T373875

Author: alistair3149

skinStyles/extensions/DiscussionTools/ext.discussionTools.ReplyWidget.less

@@ -6,6 +6,19 @@
  * Version: REL1_43
 */
 
+// T373875: Use fixed font size for DiscussionTools ReplyWidget
+.ext-discussiontools-ui-newTopic,
+.ext-discussiontools-ui-replyWidget {
+	font-size: 0.875rem;
+	line-height: 1.5714285;
+}
+
+.ext-discussiontools-ui-replyWidget-bodyWrapper,
+.ext-discussiontools-ui-newTopic-sectionTitle-field > .oo-ui-fieldLayout-body {
+	font-size: var( --font-size-medium );
+	line-height: var( --line-height-medium );
+}
+
 .ext-discussiontools-ui-replyWidget {
 	&-preview {
 		&::before {

skinStyles/extensions/DiscussionTools/ext.discussionTools.init.styles.less

@@ -6,6 +6,14 @@
  * Version: REL1_43
  */
 
+// T373875: Use fixed font size for DiscussionTools UI elements
+.ext-discussiontools-init-section-bar,
+.ext-discussiontools-init-replybutton.oo-ui-buttonElement,
+.ext-discussiontools-init-section-subscribe,
+.ext-discussiontools-init-section-subscribeButton {
+	font-size: 0.875rem;
+}
+
 .ext-discussiontools-visualenhancements-enabled {
 	h2.ext-discussiontools-ui-newTopic-sectionTitle {
 		font-size: var( --font-size-xx-large );

skinStyles/extensions/VisualEditor/ext.visualEditor.core.less

@@ -8,6 +8,15 @@
 
 @import '../../../resources/variables.less';
 
+// T373875: Use fixed font size for VE UI elements
+.ve-init-mw-desktopArticleTarget-toolbar,
+.ve-init-mw-desktopArticleTarget-toolbarPlaceholder,
+.ve-ui-overlay-local,
+.ve-ui-overlay-global,
+.ve-ui-sidebarDialogWindowManager {
+	font-size: 0.875rem;
+}
+
 .ve-ui-toolbar > .oo-ui-toolbar-bar {
 	/* Fix z-index */
 	z-index: @z-index-sticky;