Improve issue history dialog and make poster can delete their own history (#27323)

Fix #27313 (see the comment)

And some UI improvements:

### Before


![image](https://github.com/go-gitea/gitea/assets/2114189/420a314d-8f34-4e30-a557-f41cf4f0d2f2)


![image](https://github.com/go-gitea/gitea/assets/2114189/60ca0be4-b55e-4e65-be73-fd53e0d4fc36)


### After


![image](https://github.com/go-gitea/gitea/assets/2114189/d354f815-5a0c-4e63-8d59-d03ed344dbea)


![image](https://github.com/go-gitea/gitea/assets/2114189/6ef437a4-aa6f-4917-a260-00625ee71e79)


![image](https://github.com/go-gitea/gitea/assets/2114189/9d88a36c-616b-4dc9-8c6b-76adaad8acf6)

web_src/css/repo.css

@@ -2578,12 +2578,14 @@ tbody.commit-list {
 
 .comment-diff-data {
   background: var(--color-code-bg);
+  min-height: 12em;
   max-height: calc(100vh - 10.5rem);
   overflow-y: auto;
 }
 
 .comment-diff-data pre {
   line-height: 18px;
+  margin: 1em;
   white-space: pre-wrap;
   word-break: break-all;
   overflow-wrap: break-word;