NXP-15315 contributable transient file creation and thread execution handling

Conflicts:
	nuxeo-runtime-test/src/main/java/org/nuxeo/runtime/test/NXRuntimeTestCase.java
	nuxeo-runtime/src/main/resources/META-INF/MANIFEST.MF
NXP-15315 backport thread and file events handling to 5.8