Reorganize bottom menu config panels (#6131)

Mostly for the PDF bottom menu.
- Reorganize by topic, trying to limit the number
  of widgets per panel to 4.
- Re-order some toggles from low to high ('off' then 'on').
- Show font size as number instead of a list of "Aa".
- PDF: add more font size values, and increase usable
  contrast values.
- Add help_text to most PDF toggle titles.
- CRE line spacing: increase fine tuning min and max.
Also avoid zoom advice messages on book load.

frontend/ui/data/strings.lua

@@ -13,10 +13,9 @@ S.T_PAGE_MARGIN = _("Top Margin")
 S.B_PAGE_MARGIN = _("Bottom Margin")
 S.SYNC_T_B_PAGE_MARGINS = _("Sync T/B Margins")
 S.LINE_SPACING = _("Line Spacing")
-S.COLUMNS = _("Columns")
+S.DOCUMENT_COLUMNS = _("Document Columns")
 -- @translators Text alignment. Options given as icons: left, right, center, justify.
 S.TEXT_ALIGN = _("Alignment")
-S.FONTSIZE_FINE_TUNING = _("Fine Tuning")
 S.FONT_SIZE = _("Font Size")
 S.CONTRAST = _("Contrast")
 -- @translators Reflow text.
@@ -42,6 +41,7 @@ S.EMBEDDED_FONTS = _("Embedded Fonts")
 S.BLOCK_RENDERING_MODE = _("Render Mode")
 S.WRITING_DIR = _("Writing Direction")
 S.PROGRESS_BAR = _("Progress Bar")
+S.ALT_STATUS_BAR = _("Alt Status Bar")
 -- @translators If OCR is unclear, please see https://en.wikipedia.org/wiki/Optical_character_recognition
 S.FORCED_OCR = _("Forced OCR")
 S.HW_DITHERING = _("Dithering")
@@ -91,8 +91,6 @@ S.RTL = _("RTL")
 S.TBRTL = _("TBRTL")
 -- @translators TBLTR is top-to-bottom-left-to-right, which is a traditional Chinese/Japanese writing direction.
 S.TBLTR = _("TBLTR")
-S.FULL = _("full")
-S.MINI = _("mini")
 S.LEFT = _("left")
 S.CENTER = _("center")
 S.RIGHT = _("right")