Move all inline tests to /test directories

Since the original ACT tests grew up alongside the code, a lot of them are currently mixed in with the code they test in src. This is awkward because:

it pulls in overhead from supporting said tests even when not running the tests;
with #111, it actually starts pulling in noticeable dependency requirements that the /src directories shouldn't be pulling in.

This issue, then, tracks the gradual movement of ACT's expect tests to separate test-only libraries in /LIBRARY_NAME/test. Below is a tick-list of libraries to check off when no more /src tests exist. (This list is correct as of master).

[ ] abstract
[ ] asm
[ ] c_lang
[ ] c_mini
[ ] common
[ ] compiler
[x] config
[x] delitmus
[x] fuzz
[x] language
[x] litmus
[ ] machine
[x] plumbing
[ ] sanitiser
[ ] sim
[x] sim_herd
[x] sim_herdtools_common
[x] sim_litmus
[ ] toplevel
[x] utils
[ ] x86

c4-project / c4f

Move all inline tests to /test directories #112