Issues with Hydra

This is a collection of issues which we observe regarding to Hydra itself:

### Killed
e.g. execution ends with something like
```
Killed /nix/store/vkgk1hqmaqp5azfhmqzs44vrdv2lv0n0-ouroboros-network-framework-test-sim-tests-0.9.0.0/bin/sim-tests
```

* https://ci.iog.io/build/1269908
* https://ci.iog.io/build/1307082

### Possibly not delivered notification to GitHub

* https://github.com/input-output-hk/ouroboros-network/pull/4684/checks?check_run_id=17391733221

### Timed out

e.g. garbage collection kicked in
```
Server2
unidirectional Sim: OK (0.38s)
+++ OK, passed 100 tests.
bidirectional Sim: OK (0.53s)
+++ OK, passed 100 tests.
running auto-GC to free 43106246656 bytes
waiting for the big garbage collector lock...
finding garbage collector roots...
deleting garbage...
deleting '/nix/store/m79vxg2f70a3s2gcwlhn4mwpa3mrh4jx-python3.10-dmgbuild-1.6.1-rc1'
...
```

* https://ci.iog.io/build/1307123
* https://ci.iog.io/build/1310649

Sometimes things time out even though the tests finished:
* https://ci.iog.io/build/1348114/nixlog/1

### Post Build Hook

```
All 34 tests passed (20.02s)
post-build-hook: upload /nix/store/rxsan1q26sai3sdpl1jdq7bn1ka0n77a-ouroboros-network-framework-test-sim-tests-0.9.0.0-check
post-build-hook: 286722
```

* https://ci.iog.io/build/1383839/nixlog/2

### Nix GC

Sometimes `nix` `gc` is interfereing:

```
... (test output)
running auto-GC to free 43083169792 bytes
waiting for the big garbage collector lock...
finding garbage collector roots...
deleting garbage...
deleting '/nix/store/xxxx8ykvzipwpbc8wpkp08b0akzsnls5-fgl-lib-fgl-5.8.1.1-data'
... (more `deleting ...` lines)
```

* https://ci.iog.io/build/1439431/nixlog/2

### Other
_provide a new category if it doesn't fit into an existing one_