runtime: add new dodeltimer and dodeltimer0 functions
The dodeltimer function removes a timer from a heap. The dodeltimer0
function removes the first timer from a heap; in the old timer code
this common special case was inlined in the timerproc function.
Updates #27707
Change-Id: I1b7c0af46866abb4bffa8aa4d8e7143f9ae8f402
Reviewed-on: https://go-review.googlesource.com/c/go/+/171834
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Michael Knyszek <mknyszek@google.com> Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>