refactor(ui5-li, ui5-li-custom): rename classes

[ilhan007]

Rename classes for better consistency - StandardListItem has been renamed to ListItemStandard, and CustomListItem has been renamed to `ListItemCustom.

BREAKING CHANGE: StandardListItem has been renamed to ListItemStandard, and CustomListItem has been renamed to ListItemCustom. If you previously imported the classes as follows:

import StandardListItem from "@ui5/webcomponents/StandardListItem.js";
import CustomListItem from "@ui5/webcomponents/CustomListItem.js";

now you must change imports to:

import ListItemStandard from "@ui5/webcomponents/ListItemStandard.js";
import ListItemCustom from "@ui5/webcomponents/ListItemCustom.js";

Related to: #8461