Move rarely-used tests into 'code coverage' tests (#2848)

These tests will still be executed in CI/CD pipelines, but will not be
executed locally when doing 'git push' with pre-commit installed.

Author: ipspace

tests/coverage.sh

@@ -1,4 +1,4 @@
 #!/bin/bash
 coverage erase
-PYTHONPATH="../" coverage run --source ../netsim -m pytest
+PYTHONPATH="../" coverage run --source ../netsim -m pytest -k 'coverage or error'
 coverage html

tests/errors/device-data-invalid.log renamed to tests/coverage/errors/device-data-invalid.log

@@ -0,0 +1,3 @@
+IncorrectType in yaml: Duplicate section in YAML file: nodes
+Fatal error in netlab: Cannot read YAML from coverage/errors/duplicate-yaml-section.yml: Duplicate section nodes
+  in "coverage/errors/duplicate-yaml-section.yml", line 2, column 1