Allows configuring the watchdog signal (with a default of SIGABRT).
This allows an alternative to SIGABRT when coredumps are not desirable.
Appropriate references to SIGABRT or aborting were renamed to reflect
more liberal watchdog signals.
Closes#8658
The docs/ directory is special in GitHub, since it can be used to serve GitHub
Pages from, so there's a benefit to switching to it in order to expose it
directly as a website.
Updated references to it from the documentations themselves, from the
CONTRIBUTING.md file and from Meson build files.