Vectorize overlap and search methods for better performance (#69)

- Do not delete NCLS index for repeated queries. 
- I *think* this also fixes a bug in `reduce` operation which modifies `self`. 
- More consistent responses for count & find overlap methods.
- Update tests.

setup.cfg

@@ -50,7 +50,7 @@ python_requires = >=3.8
 install_requires =
     importlib-metadata; python_version<"3.8"
     biocframe>=0.5.3,<0.6.0
-    iranges[optional]>=0.2.2,<0.3.0
+    iranges[optional]>=0.2.3,<0.3.0
     biocutils>=0.1.3,<0.2.0
     numpy