As we already rely on the GlyphItem's font instance, consequently
this removes the SalGraphics GlyphItem based functions. Also
unifies the glyph bound rect cache handling.

An interesting aspect is the rotated glyph bounding box handling
moved from CairoTextRender to FreetypeFont. It doesn't look like
an implementation detail for Cairo, so it may have been a bug.

Change-Id: I81bbb5d8ee98fb77a1eee05568c456f9e4553023
Reviewed-on: https://gerrit.libreoffice.org/62503
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>