[LTS 18.4] USS Bad suggestions

Environment: **2018.4 LTS**

Valid (overwrites `padding-bottom`, `padding-top`, ...)
```css
Button {
padding-right: 1px;
padding-top: 1px;
padding-left: 1px;
padding-bottom: 1px;
}
```

Invalid (doesn't overwrite `padding-bottom`, `padding-top`, ...)
```css
Button {
padding: 1px
}
```

Obviously like in CSS you would shorthand the first block to `padding: 1px`. Sadly this does not work. Rider is still suggesting this.

This is fixed in newer versions (at least 19.3) but LTS still has a relevant user base.

Start by reproducing the USS padding shorthand behavior in Unity 2018.4 and compare it with the fixed behavior reported in version 19.3. Trace the suggestion shown for the `padding` property and confirm that the shorthand is no longer recommended when it does not overwrite the individual padding properties.

Written by the indexing model from the issue text.