Add benchmarking test suite and greatly improve performance in a few cases (#948)

* Add benchmarking test suite

* Improve amortized time of model relation loads with a large number of rows

* Improve performance of loading models with many related models

* Improve performance of loading models with many related models to O(N)ish

* Fix bug where N model creation with shared related model would build in N^2 time

* Lower blocking time for queryset results

* Add docstrings and streamline hash code

Co-authored-by: haydeec1 <Eric.Haydel@jhuapl.edu>

tests/test_relations/test_weakref_checking.py

@@ -0,0 +1,52 @@
+from typing import Optional, Type
+
+import databases
+import pytest
+import pytest_asyncio
+import sqlalchemy
+
+import ormar
+from tests.settings import DATABASE_URL
+
+database = databases.Database(DATABASE_URL)
+metadata = sqlalchemy.MetaData()
+
+
+class Band(ormar.Model):
+    class Meta:
+        tablename = "bands"
+        metadata = metadata
+        database = database
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=100)
+
+
+class Artist(ormar.Model):
+    class Meta:
+        tablename = "artists"
+        metadata = metadata
+        database = database
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=100)
+
+    band: Band = ormar.ForeignKey(Band)
+
+
+def test_weakref_init():
+    band = Band(name="Band")
+    artist1 = Artist(name="Artist 1", band=band)
+    artist2 = Artist(name="Artist 2", band=band)
+    artist3 = Artist(name="Artist 3", band=band)
+
+    del artist1
+    Artist(
+        name="Artist 2", band=band
+    )  # Force it to check for weakly-referenced objects
+    del artist3
+
+    band.artists  # Force it to clean
+
+    assert len(band.artists) == 1
+    assert band.artists[0].name == "Artist 2"