Introduce form-styles

To make sharedStyles smaller, since they add a cost in rendering.

To resolve TODO introduced by comment:
https://gerrit-review.git.corp.google.com/c/gerrit/+/344128/comment/083587cc_f48f08e8/

Release-Notes: skip
Change-Id: I46402ad50018288aea893d28d999579372ef686a
diff --git a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
index 6ca4702..7499082 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
@@ -72,6 +72,7 @@
   CommentModel,
   commentModelToken,
 } from '../gr-comment-model/gr-comment-model';
+import {formStyles} from '../../../styles/form-styles';
 
 // visible for testing
 export const AUTO_SAVE_DEBOUNCE_DELAY_MS = 2000;
@@ -322,6 +323,7 @@
 
   static override get styles() {
     return [
+      formStyles,
       sharedStyles,
       modalStyles,
       css`