The defaults for test timeouts in meson is 30 seconds. That is not long
enough when running

  $ NMTST_USE_VALGRIND=1 ninja -C build test

Note that meson supports --timeout-multiplier, and automatically
increases the timeout when running under valgrind. However, meson
does not understand that we are running tests under valgrind via
NMTST_USE_VALGRIND=1 environment variable.

Timeouts are really not expected to be reached and are a mean of last
resort. Hence, increasing the timeout to a large value is likely to
have no effect or to fix test failures where the timeout was too rigid.
It's unlikely that the test indeed hangs and the increase of timeout
causes a unnecessary increase of waittime before aborting.