[TECHNICAL-SUPPORT] LPS-23717 Custom scoped portlet title is modified during layout update

Hey Tamás,

Unfortunately, we cannot test/reproduce the issue on trunk, because the add portlet functionality is broken.

This is the latest commit on which I was able to work: https://github.com/liferay/liferay-portal/commit/73ac90433c2504050a4d869a36c49da96fafb312

I used this state as HEAD for this pull. However, the codes I touched are the same on the latest trunk as well, so it can be easily merged.

== About my changes

1. LPS-23717 Rename method to getPortletCustomTitle. It is more expressive: I think this method name is more expressive than the old one, and it follows the pattern of the other method in PortletConfigurationUtil #getPortletCustomCSSClassName.

I have searched for all occurrences of the old method name in the source & have refactored them.

2. LPS-23717 Preserve portlet custom titles on layout rename: LayoutLocalServiceUtil.updateScopedPortletNames() (line 2347) is called only from the method UpdateLayoutAction#updateName(HttpServletRequest). We should preserve the portlet's custom title (if exists) on layout rename.

Regards,
Tibor