change(aurweb): add parallel tests and improve aurweb.db

This change utilizes pytest-xdist to perform a multiproc test
run and reworks aurweb.db's code. We no longer use a global
engine, session or Session, but we now use a memo of engines
and sessions as they are requested, based on the PYTEST_CURRENT_TEST
environment variable, which is available during testing.

Additionally, this change strips several SQLite components
out of the Python code-base.

SQLite is still compatible with PHP and sharness tests, but
not with our FastAPI implementation.

More changes:
------------
- Remove use of aurweb.db.session global in other code.
- Use new aurweb.db.name() dynamic db name function in env.py.
- Added 'addopts' to pytest.ini which utilizes multiprocessing.
    - Highly recommended to leave this be or modify `-n auto` to
      `-n {cpu_threads}` where cpu_threads is at least 2.

Signed-off-by: Kevin Morris <kevr@0cost.org>

test/test_api_rate_limit.py

@@ -3,19 +3,18 @@ import pytest
 from sqlalchemy.exc import IntegrityError
 
 from aurweb import db
-from aurweb.db import create
 from aurweb.models.api_rate_limit import ApiRateLimit
-from aurweb.testing import setup_test_db
 
 
 @pytest.fixture(autouse=True)
-def setup():
-    setup_test_db("ApiRateLimit")
+def setup(db_test):
+    return
 
 
 def test_api_rate_key_creation():
     with db.begin():
-        rate = create(ApiRateLimit, IP="127.0.0.1", Requests=10, WindowStart=1)
+        rate = db.create(ApiRateLimit, IP="127.0.0.1", Requests=10,
+                         WindowStart=1)
     assert rate.IP == "127.0.0.1"
     assert rate.Requests == 10
     assert rate.WindowStart == 1
@@ -23,19 +22,15 @@ def test_api_rate_key_creation():
 
 def test_api_rate_key_ip_default():
     with db.begin():
-        api_rate_limit = create(ApiRateLimit, Requests=10, WindowStart=1)
+        api_rate_limit = db.create(ApiRateLimit, Requests=10, WindowStart=1)
     assert api_rate_limit.IP == str()
 
 
 def test_api_rate_key_null_requests_raises_exception():
     with pytest.raises(IntegrityError):
-        with db.begin():
-            create(ApiRateLimit, IP="127.0.0.1", WindowStart=1)
-    db.rollback()
+        ApiRateLimit(IP="127.0.0.1", WindowStart=1)
 
 
 def test_api_rate_key_null_window_start_raises_exception():
     with pytest.raises(IntegrityError):
-        with db.begin():
-            create(ApiRateLimit, IP="127.0.0.1", Requests=1)
-    db.rollback()
+        ApiRateLimit(IP="127.0.0.1", Requests=1)