Not possible to customize the label of the search

Problem/Motivation

It is currently not possible to modify the label of the search input. Since it is read by screen readers when not visible, it is useful to be able to configure it.
Add also the possibility to control the visibility of the label, so if someone wants to actually display it, they can actually do it without code. It is pretty useful for theme that are using theme that use the label as the "placeholder" and move it to the top of input on focus.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes