Checking for overflow of integer addition by comparing against one of
the arguments of the addition does not work when the result of the
addition is automatically promoted to a larger type.
Fix by using an explicit cast to make sure that the result of the
addition is not implicitly converted to a larger type.
19212: shell/rtc: use rtc_tm_normalize() to sanitize input r=benpicco a=benpicco
19360: gcoap: make use coap_build_reply() in gcoap_resp_init() r=benpicco a=benpicco
19401: shell/cmds: add genfile command r=benpicco a=benpicco
19645: sys/isrpipe: Replace xtimer with ztimer_usec r=benpicco a=MrKevinWeiss
### Contribution description
Getting ready for the xtimer dep.
### Testing procedure
Green murdock, there is no explicit test for isrpipe but since it runs xtimer compat it should operate the same.
### Issues/PRs references
19720: tests: remove unnecessary use of floating point r=benpicco a=benpicco
Co-authored-by: Benjamin Valentin <benjamin.valentin@bht-berlin.de>
Co-authored-by: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Co-authored-by: MrKevinWeiss <weiss.kevin604@gmail.com>
Co-authored-by: Benjamin Valentin <benpicco@beuth-hochschule.de>
19693: sys/color: extend unittest and fix module r=maribu a=kfessel
### Contribution description
this extends the unittest for sys_color testing more colors
### Testing procedure
```
RIOT_tree/tests/unittests$ make tests-color test
```
will fail since our `rgb2hsv` implementation is wrong (or is using an other colorspace than hsv2rgb (without documenting))
the new `hsv2rgb` test will succeed
### Issues/PRs references
#19614 was the reason i had a look at this
#1315 added the rgb2hsv and hsv2rgb function
#9940 added the test for black special case
https://www.vagrearg.org/content/hsvrgb << some optimization for that function (avoiding float)
Co-authored-by: Karl Fessel <karl.fessel@ovgu.de>
