examples: migrate to XFA SHELL_COMMAND

[mguetschow]

Contribution description

Migrate all remaining examples to using the XFA SHELL_COMMAND instead of the statically allocated list (often with extern function declarations) in main.c.

Testing procedure

CI should find bugs.

[riot-ci]

Murdock results

✔️ PASSED

8f5f268 examples: migrate to XFA SHELL_COMMAND

Success	Failures	Total	Runtime
292	0	292	02m:46s

Artifacts

• Documentation preview

[maribu]

I like this one :) Thx!

Some comments inline. Feel free to squash at will and hit merge.

[mguetschow]

Oh, this one is interesting:

In file included from main.c:27:
main.c:91:23: error: expected '=', ',', ';', 'asm' or '__attribute__' before '-' token
   91 | SHELL_COMMAND(riotboot-hdr, "Print current slot header", cmd_print_riotboot_hdr);

So using SHELL_COMMAND here would actually require changing the command name. I guess that would be fine for an example?

[maribu]

Yes, it was brought up that SHELL_COMMAND() would limit shell cmd names to names that after being prefixed end up as valid C identifier names, unless we add an extra parameters to SHELL_COMMAND() to explicitly specify the C identifier in addition to the shell cmd name. There was widespread support for the easier interface, even if we have to convert e.g. every minus to an underscore.

[mguetschow]

Okay, changed the functions to static, changed the two shell command names, and squashed. Thanks for your review!