Fix frozen delta watermark and add error stats, lazy source, concurrent disk reads, and per-engine config

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "sqlmem"
-version = "1.7.0"
+version = "1.8.0"
 description = ""
 authors = [
     {name = "jan.doubravsky@gmail.com"}
@@ -25,3 +25,11 @@ dev = [
     "ruff (>=0.15.15,<0.16.0)",
     "mypy (>=2.1.0,<3.0.0)"
 ]
+
+[tool.pytest.ini_options]
+filterwarnings = [
+    # The SQLite test source binds the delta watermark as a real datetime via
+    # sqlite3's legacy adapter (deprecated in 3.12). Production sources are
+    # pyodbc, which binds datetimes natively, so this only affects the tests.
+    "ignore:The default datetime adapter is deprecated:DeprecationWarning",
+]