New approach to full bleed printing etc.

[Omikhleia]

My approach of https://github.com/sile-typesetter/sile/pull/1470 was quite right on everything, except one: the new constraint on the "page" frame.

It all becomes much simpler considering paper vs. page and bleed are actually an outputter issue. We don't care of true paper size and bleed if it doesn't make it to print! And suddenly we don't have to tweak / reconstrain frames... See comment Recap below.

To do

• [x] outputter: de-correlate frame coordinate cursor from outputter cursor
  • [x] images
  • [x] text
  • [x] svg
  • [x] debug hbox (but this one already had issues independently) - analyzed, easy --> typesetter issue
  • other? Apparently no, but...
    • [x] packages: Check why some pdf package commands wrap their content in a box where it doesn't seem necessary
• [x] packages: cropmarks
• [x] packages: background
• [x] packages: other packages toying with libpdftex directly = bad separation of concerns...
  • [x] pdf = breaks - analyzed, easy
  • pdfstructure = no problem (no coordinates)
  • [x] rotate = breaks - analyzed, easy
  • [x] scalebox = breaks - analyzed, easy
  • textsubsuper = breaks - should use scalebox now, to avoid code duplication = tracked as https://github.com/Omikhleia/textsubsuper.sile/issues/3
• [x] classes: base class options
• [x] tests
  • [x] Check dedicated test
  • [x] (regression testing) Compile resilient manual (with SILE 0.14.10 + this silex PR)
  • [x] (regression testing) Compile SILE manual (with SILE 0.14.10 + backport to SILE)

Checks

[Omikhleia]

Recap

Related SILE issues:

• https://github.com/sile-typesetter/sile/issues/1285
• https://github.com/sile-typesetter/sile/issues/1439
• https://github.com/sile-typesetter/sile/issues/916
• https://github.com/sile-typesetter/sile/issues/902
• https://github.com/sile-typesetter/sile/issues/427 (not addressed here, but annotated with comments)