refactor: globals in tests (#5298)

Refactor tests to have less globals.

This will allow to hopefully write more complex tests for our new metric
collection requirements in #5297. Includes reverted work from #4761
related to test globals.

Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: MMeent <matthias@neon.tech>

test_runner/fixtures/httpserver.py

@@ -0,0 +1,45 @@
+from typing import Tuple
+
+import pytest
+from pytest_httpserver import HTTPServer
+
+# TODO: mypy fails with:
+#  Module "fixtures.neon_fixtures" does not explicitly export attribute "PortDistributor"  [attr-defined]
+# from fixtures.neon_fixtures import PortDistributor
+
+# compared to the fixtures from pytest_httpserver with same names, these are
+# always function scoped, so you can check and stop the server in tests.
+
+
+@pytest.fixture(scope="function")
+def httpserver_ssl_context():
+    return None
+
+
+@pytest.fixture(scope="function")
+def make_httpserver(httpserver_listen_address, httpserver_ssl_context):
+    host, port = httpserver_listen_address
+    if not host:
+        host = HTTPServer.DEFAULT_LISTEN_HOST
+    if not port:
+        port = HTTPServer.DEFAULT_LISTEN_PORT
+
+    server = HTTPServer(host=host, port=port, ssl_context=httpserver_ssl_context)
+    server.start()
+    yield server
+    server.clear()
+    if server.is_running():
+        server.stop()
+
+
+@pytest.fixture(scope="function")
+def httpserver(make_httpserver):
+    server = make_httpserver
+    yield server
+    server.clear()
+
+
+@pytest.fixture(scope="function")
+def httpserver_listen_address(port_distributor) -> Tuple[str, int]:
+    port = port_distributor.get_port()
+    return ("localhost", port)