Fix color codes used even when --color never is specified

[cschreib]

This PR fixes #147:

• The registry class now forwards its with_color option to the print_help() function, so ./tests --color never --help prints the help text without color codes.
• The command-line parser now parses arguments in two passes. The first pass looks only at color options, silently ignoring any problem, then changes the color configuration as specified. The second pass looks again at all options, and reports any problem using the color options configured in the first pass. This means that, for example, ./tests --color never --verbosity babbling will report the unknown babbling value without using color codes.

Note that, in both cases, argument ordering remains irrelevant, so --color never --help and --help --color never produces the same output.

[codecov]

Codecov Report

Merging #148 (fa587c0) into main (770286e) will increase coverage by 0.10%.
Report is 2 commits behind head on main.
The diff coverage is 72.13%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #148      +/-   ##
==========================================
+ Coverage   93.67%   93.78%   +0.10%     
==========================================
  Files          27       27              
  Lines        1597     1624      +27     
==========================================
+ Hits         1496     1523      +27     
  Misses        101      101              

Files	Coverage Δ
include/snitch/snitch_cli.hpp	100.00% <ø> (ø)
src/snitch_registry.cpp	94.88% <100.00%> (ø)
src/snitch_cli.cpp	83.87% <71.66%> (+2.73%)	⬆️

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