valgrind: update to 3.20.0

Changes in this update includes:
* The option "--vgdb-stop-at=event1,event2,..." accepts the new value
  abexit. This indicates to invoke gdbserver when your program exits
  abnormally (i.e. with a non zero exit code).
* Fix Rust v0 name demangling.
* The Linux rseq syscall is now implemented as (silently) returning
  ENOSYS.
* Add FreeBSD syscall wrappers for __specialfd and __realpathat.
* Remove FreeBSD dependencies on COMPAT10, which fixes compatibility
  with HardenedBSD
* The option --enable-debuginfod=<no|yes> [default: yes] has been added
  on Linux.
* More DWARF5 support as generated by clang14.

Drop the patch 0001-Fix-drd-tests-shared_timed_mutex.cpp.patch which was
merged upstream.

ptest result:
System   Pass  Fail  Skip
x86-64   717   0     20

Signed-off-by: Zheng Qiu <zheng.qiu@windriver.com>
Signed-off-by: Randy MacLeod <randy.macleod@windriver.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>