Log Message:
tex-tcolorbox{,-doc}: update to 5.1.1

5.1.1
### Changed
- Some documentation improvements
- Library `xparse` removed from settings `many` and `most`
- Slight implemenation change for `\newtcbtheorem` and `\renewtcbtheorem`

### Fixed
- Regression bug introduced with v5.0.0 2021-12-16
   Instead of `beforeafter skip balanced`, `autoparskip` was set as default,
   restoring the situation before v4.40 (with some inconsistencies)

5.1.0
 ### Added
 - Options wrapping `\tl_if_blank:nTF` and `\tl_if_empty:nTF`
 - Options to insert code at begin and end of floats
 - Library `skins`: overlap of lower part for `bicolor`, `tile`, and `beamer`
     made configurable
 - Library `documentation`: package warning, if `imakeidx` is loaded after the
     library is loaded
 - Library `documentation`: gather index LaTeX macros and configure gathering

 ### Changed
- Required latex2e specified `\NeedsTeXFormat{LaTeX2e}[2020/10/01]`
- Documentation: comment `default setting` for `every box on higher layers`
- Documentation: hyperlinking keys and commands where not already done inside
    the listings section
- All contents of library `xparse` are moved to the `tcolorbox` main package and
    to libraries `listings` and `fitting` respectively. `xparse` now only loads
    the package `xparse`
- Internal implementation of all `\new*` commands, e.g. `\newtcolorbox` changed.
    Note that a missing backlash for `tcbox`-like commands
    e.g. `\newtcbox{mybox}` instead of `\newtcbox{\mybox}` is no longer tolerated.

### Fixed
- With `parbox=false`, `before skip` was ignored in inner box