ostest/hrtimer: align hrtimer test and add threaded hrtimer tests

[wangchdo]

Summary

1. align hrtimer callback declaration with latest update of hrtimer
2. Add threaded hrtimer tests

Impact

Hritmer ostest improvements, no impact to any other functions

apache/nuttx#18025 rely on this PR to fix the CI build issue

Testing

ostest passed with hrtimer enabled:

rv-virt:smp64

NuttShell (NSH)
nsh> 
nsh> uname -a
NuttX 0.0.0 3485d61db2-dirty Jan 20 2026 11:42:50 risc-v rv-virt
nsh> 
nsh> ostest

(...)

user_main: hrtimer test

End of test memory usage:
VARIABLE  BEFORE   AFTER
======== ======== ========
arena     1fc0a00  1fc0a00
ordblks         9       11
mxordblk  1f71c68  1f50cd0
uordblks    15c90    27320
fordblks  1faad70  1f996e0

Final memory usage:
VARIABLE  BEFORE   AFTER
======== ======== ========
arena     1fc0a00  1fc0a00
ordblks         1       11
mxordblk  1fb5908  1f50cd0
uordblks     b0f8    27320
fordblks  1fb5908  1f996e0
user_main: Exiting
ostest_main: Exiting with status 0
nsh>