Fix: build and help

[dragonmux]

In this PR we do two things: We fix the build which is broken by an improper project option; and implement better, more discoverable, help care of some companion changes in substrate.

For the first part of this, the project() statement in the top-level meson.build had b_debug as an option specified which is wrong - the option is actually called b_ndebug.

For the second part, we have introduced a new optionsRoot_t to the substrate command line parser types, and implemented a whole lot more help generation machinery which allows it to generate the full help text automatically. This is then backed by companion changes here to make use of the new types and machinery to provide help text generation for cheap while also properly recursing into option set alternations so that the user can get action-specific help as well.

The -h/--help option is now a global option with this, meaning it is allowed to appear at every level of parsing.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 0.00%. Comparing base (6ce3273) to head (ea1fa34).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
src/bmpflash.cxx	0.00%	7 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main     #15   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files         34      34           
  Lines       1834    1797   -37     
  Branches     572     573    +1     
=====================================
+ Misses      1798    1761   -37     
  Partials      36      36           

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[esden]

LGTM