Add mixin to adjust padding for multi-line material input and remove the ::ng-deep usage in awn conversions.

PiperOrigin-RevId: 207051240

Author: cissyshi

lib/material_input/_mixins.scss

@@ -215,3 +215,15 @@
     }
   }
 }
+
+/// Changes the padding of the multiline material input.
+@mixin multiline-material-input-padding($padding) {
+  ::ng-deep {
+    .label,
+    .mirror-text,
+    .textarea {
+      box-sizing: border-box;
+      padding: $padding;
+    }
+  }
+}