Add recovery tests

In depth testing of the recovery mechanism during a rolling restart.
Based on org.elasticsearch.upgrades.RecoveryIT.java

setup.py

@@ -30,7 +30,7 @@ def read(filename):
     packages=['crate.qa'],
     namespace_packages=['crate'],
     install_requires=[
-        'cr8>=0.16.0',
+        'cr8>=0.20.0',
         'Cython',
         'asyncpg>=0.18.2, < 0.20',
         'pyodbc',

src/crate/qa/tests.py

@@ -29,6 +29,14 @@
 ) + tuple(glob('/Library/Java/JavaVirtualMachines/jdk*1.8*/Contents/Home'))
 
 
+class UpgradePath(NamedTuple):
+    from_version: str
+    to_version: str
+
+    def __repr__(self):
+        return f'{self.from_version} -> {self.to_version}'
+
+
 def prepare_env(java_home_candidates: Iterable[str]) -> dict:
     for candidate in filter(os.path.exists, java_home_candidates):
         return {'JAVA_HOME': candidate}