test: each app keeps its tests in a tests package

131 test modules sat next to the code they test; instances alone had
51 of them beside views.py and utils.py. They move into a
tests/ package per app, and the JavaScript checks into
webvirtcloud/tests/js. Each non-empty tests.py becomes tests/test_views.py;
the empty generated stubs are removed.

Imports of the app's own modules become absolute, paths built from
__file__ go one level up, the live helper is instances.tests.livetest,
and coverage omits */tests/*. The suite discovers the same 960 tests as
before.

webvirtcloud/tests/js/poll.test.js

@@ -1,5 +1,5 @@
 // Behaviour of static/js/poll.js with a fake clock, document and jQuery promise.
-// Run by webvirtcloud/test_poll_js.py: node poll.test.js static/js/poll.js
+// Run by webvirtcloud/tests/test_poll_js.py: node poll.test.js static/js/poll.js
 const fs = require("fs");
 const assert = require("assert");
 

webvirtcloud/tests/test_child_processes.py

@@ -9,7 +9,7 @@ import sys
 import unittest
 from pathlib import Path
 
-ROOT = Path(__file__).resolve().parent.parent
+ROOT = Path(__file__).resolve().parent.parent.parent
 
 CHECK = """
 import signal, subprocess

webvirtcloud/tests/test_instance_tabs_js.py

@@ -15,7 +15,7 @@ class InstanceTabsTestCase(unittest.TestCase):
     @unittest.skipUnless(shutil.which("node"), "node is not installed")
     def test_instance_tabs_js(self):
         result = subprocess.run(
-            ["node", str(BASE / "webvirtcloud/js_tests/instance_tabs.test.js"), str(BASE / "static/js/instance_tabs.js")],
+            ["node", str(BASE / "webvirtcloud/tests/js/instance_tabs.test.js"), str(BASE / "static/js/instance_tabs.js")],
             capture_output=True,
             text=True,
             timeout=60,

webvirtcloud/tests/test_poll_js.py

@@ -18,7 +18,7 @@ class PollTestCase(unittest.TestCase):
     @unittest.skipUnless(shutil.which("node"), "node is not installed")
     def test_poll_js(self):
         result = subprocess.run(
-            ["node", str(BASE / "webvirtcloud/js_tests/poll.test.js"), str(BASE / "static/js/poll.js")],
+            ["node", str(BASE / "webvirtcloud/tests/js/poll.test.js"), str(BASE / "static/js/poll.js")],
             capture_output=True,
             text=True,
             timeout=60,