sys/ztimer64: fix ztimer64_remove() not properly clearing timer struct

[kaspar030]

Contribution description

ztimer64 wasn't properly clearing a removed timer struct, but depended on that for it's ztimer64_is_set().

This PR adds a fix, and a regression test.

regression test output with the fix reverted:

main(): This is RIOT! (Version: 2022.04-devel-568-g33dae8-fix_ztimer64_remove)
Help: Press s to start test, r to print it is ready
rs
READY
START
.......
ztimer64_tests.test_ztimer64_remove_clear (tests/unittests/tests-ztimer64/tests-ztimer64-core.c 238) !ztimer64_is_set(&timer)

run 7 failures 1

Testing procedure

CI tests this now. :)

Issues/PRs references

Found with #17365.

[fjmolinas]

Nice catch! Thanks!

[fjmolinas]

Independent build failure

--- result: BUILD FAILED!

--- [JUMP TO FIRST ERROR OUTPUT](https://ci.riot-os.org/RIOT-OS/RIOT/17720/e9227153c0b468811679f31750b7ee667df9169a/output.html#error0)

--- static tests: passed
-- running on worker riotbuild-0 thread 4, build number 173819.
--- can_fast_ci_run:
Currently changing modules require a full CI run

-- can_fast_ci_run.py exited non-zero

---
--- compile job results (1 failed, 106927 passed, 106928 total):

-- running on worker mobi3 thread 6, build number 111071.
make: Entering directory '/tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/examples/hello-world'
rm -rf /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/pkg-build/esp8266_sdk
make: Leaving directory '/tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/examples/hello-world'
make: Entering directory '/tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/examples/hello-world'
[INFO] cloning esp8266_sdk
Building application "hello-world" for "esp8266-esp-12x" with MCU "esp8266".

git-cache: cloning from cache. tag=commit913a06a9ac3b2f18009e8fee8f092ca9ffeccd38-2924006
[INFO] updating esp8266_sdk /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/pkg/esp8266_sdk/.pkg-state.git-downloaded
echo 913a06a9ac3b2f18009e8fee8f092ca9ffeccd38 > /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/pkg/esp8266_sdk/.pkg-state.git-downloaded
[INFO] patch esp8266_sdk
   text	   data	    bss	    dec	    hex	filename
 275656	   5284	  28592	 309532	  4b91c	/tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/hello-world.elf
esptool.py v2.4.0
Parsing CSV input...
sha1sum /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/hello-world.elf /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/hello-world.elf.bin /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/partitions.bin > /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/test-input-hash.sha1
make: Leaving directory '/tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/examples/hello-world'
make: Entering directory '/tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/examples/hello-world'
Building application "hello-world" for "esp8266-esp-12x" with MCU "esp8266".
rm -rf /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/pkg-build/esp8266_sdk

[INFO] cloning esp8266_sdk
git-cache: cloning from cache. tag=commit913a06a9ac3b2f18009e8fee8f092ca9ffeccd38-2952351
[INFO] updating esp8266_sdk /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/pkg/esp8266_sdk/.pkg-state.git-downloaded
echo 913a06a9ac3b2f18009e8fee8f092ca9ffeccd38 > /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/pkg/esp8266_sdk/.pkg-state.git-downloaded
[INFO] patch esp8266_sdk
   text	   data	    bss	    dec	    hex	filename
 275768	   5284	  28592	 309644	  4b98c	/tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/hello-world.elf
esptool.py v2.4.0
Parsing CSV input...
sha1sum /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/hello-world.elf /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/hello-world.elf.bin /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/partitions.bin > /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/test-input-hash.sha1
make: Leaving directory '/tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/examples/hello-world'
Hashes of binaries with and without Kconfig mismatch for examples/hello-world with esp8266-esp-12x
Please check that all used modules are modelled in Kconfig and enabled
rm -rf /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/pkg-build/esp8266_sdk
rm -rf /tmp/dwq.0.566681958266741/9708fce03c297ce05e3ed75e81cf3c56/build/pkg-build/esp8266_sdk
-- build directory size: 100K