`hardware_alarm` functions on wrong documentation page

[davidgiven]

Something isn't right with the documentation for the hardware_alarm functions. The timer.h page (https://raspberrypi.github.io/pico-sdk-doxygen/rp2__common_2hardware__timer_2include_2hardware_2timer_8h.html#a62098633d173c24c56c359df2e886ed2) documents only hardware_alarm_cancel() and hardware_alarm_set_target(), but none of the others. Meanwhile the hardware_timer page (https://raspberrypi.github.io/pico-sdk-doxygen/group__hardware__timer.html#gaa4c3c72008c100ca25f94b806f13f112) documents all the functions except hardware_alarm_cancel() and hardware_alarm_set_target().

I think that these two functions are incorrectly tagged somehow so that they appears in timer.h's documentation but not in `hardare_timer'.

[kilograham]

will move them to the same group as the others

[kilograham]

merged to develop