minor rtl fixes (#2595)

Author: renefloor

packages/stream_chat_flutter/lib/src/channel/channel_header.dart

@@ -181,7 +181,7 @@ class StreamChannelHeader extends StatelessWidget implements PreferredSizeWidget
               elevation: elevation,
               scrolledUnderElevation: scrolledUnderElevation,
               leading: Padding(
-                padding: EdgeInsets.only(left: context.streamSpacing.sm),
+                padding: .directional(start: context.streamSpacing.sm),
                 child: leadingWidget,
               ),
               leadingWidth: StreamAvatarSize.lg.value,
@@ -194,7 +194,7 @@ class StreamChannelHeader extends StatelessWidget implements PreferredSizeWidget
                   <Widget>[
                     if (effectiveCenterTitle)
                       Padding(
-                        padding: EdgeInsets.only(right: context.streamSpacing.sm),
+                        padding: .directional(end: context.streamSpacing.sm),
                         child: Center(
                           child: GestureDetector(
                             onTap: onImageTap,

packages/stream_chat_flutter/lib/src/channel/channel_list_header.dart

@@ -141,7 +141,7 @@ class StreamChannelListHeader extends StatelessWidget implements PreferredSizeWi
               leading: switch ((leading, user)) {
                 (final leading?, _) => leading,
                 (_, final user?) => Padding(
-                  padding: EdgeInsets.only(left: context.streamSpacing.sm),
+                  padding: .directional(start: context.streamSpacing.sm),
                   child: Center(
                     child: GestureDetector(
                       onTap: switch (onUserAvatarTap) {
@@ -161,7 +161,7 @@ class StreamChannelListHeader extends StatelessWidget implements PreferredSizeWi
                 ),
                 _ => const Empty(),
               },
-              actionsPadding: EdgeInsets.only(right: context.streamSpacing.sm),
+              actionsPadding: .directional(end: context.streamSpacing.sm),
               actions:
                   actions ??
                   [

sample_app/lib/widgets/search_text_field.dart

@@ -49,7 +49,7 @@ class SearchTextField extends StatelessWidget {
               decoration: InputDecoration(
                 prefixIconConstraints: BoxConstraints.tight(const Size(36, 24)),
                 prefixIcon: Padding(
-                  padding: EdgeInsets.only(left: spacing.md),
+                  padding: .directional(start: spacing.md),
                   child: Icon(
                     context.streamIcons.search20,
                     color: colorScheme.textTertiary,