TextWidget: small refactoring, better handle max_width (#5503)

Lots of code was doing some renderText calls to get the size
of some text string, and truncate it to some width if needed,
with or without an added ellipsis, before instantiating
a TextWidget with that tweaked text string.

This PR fixes/adds some properties and methods to TextWidget
so all that can be done by it. It makes the calling code
simpler, as they don't need to use RenderText directly.
(Additionally, when we go at using Harfbuzz for text rendering,
we'll just have to update or replace textwidget.lua without
the need to update any higher level code.)

Also:
- RenderText: removed the space added by truncateTextByWidth
  after the ellipsis, as it doesn't feel needed, and break
  right alignment of the ellipsis with other texts.
- KeyValuePage: fix some subtle size and alignment issues.
- NumberPickerWidget: fix font size (provided font size was
  not used)

frontend/ui/widget/spinwidget.lua

@@ -12,7 +12,6 @@ local InputContainer = require("ui/widget/container/inputcontainer")
 local LineWidget = require("ui/widget/linewidget")
 local NumberPickerWidget = require("ui/widget/numberpickerwidget")
 local OverlapGroup = require("ui/widget/overlapgroup")
-local RenderText = require("ui/rendertext")
 local Size = require("ui/size")
 local TextBoxWidget = require("ui/widget/textboxwidget")
 local TextWidget = require("ui/widget/textwidget")
@@ -90,24 +89,16 @@ function SpinWidget:update()
 
     local close_button = CloseButton:new{ window = self, padding_top = Size.margin.title, }
     local btn_width = close_button:getSize().w + Size.padding.default * 2
-    local title_txt_width = RenderText:sizeUtf8Text(
-        0, self.width, self.title_face, self.title_text).x
-    local show_title_txt
-    if self.width < (title_txt_width + btn_width) then
-        show_title_txt = RenderText:truncateTextByWidth(
-            self.title_text, self.title_face, self.width - btn_width)
-    else
-        show_title_txt = self.title_text
-    end
+
     local value_title = FrameContainer:new{
         padding = Size.padding.default,
         margin = Size.margin.title,
         bordersize = 0,
         TextWidget:new{
-            text = show_title_txt,
+            text = self.title_text,
+            max_width = self.width - btn_width,
             face = self.title_face,
             bold = true,
-            width = self.width,
         },
     }
     local value_line = LineWidget:new{