Add valgrind checks (memcheck, helgrind, cachegrind)

[johannes-wolf]

Runs test under various valgrind tools to detect memory and threading errors.

[github-actions[bot]]

Package	Line Rate	Branch Rate	Health
include.simfil	50%	30%	❌
src	59%	33%	➖
src.model	65%	44%	➖
Summary	57% (1676 / 2923)	33% (1502 / 4506)	➖

Minimum allowed line rate is 50%

[josephbirkner]

Looks great!