Fix manager types scope (#991)

* Fix manager types scope

* Restore incremental mode and mention in developer docs

* Separate dev mypy config and regular one

* Document config files usage

mypy.ini

@@ -1,3 +1,10 @@
+# Regular configuration file (can be used as base in other projects, runs in CI)
+
+# NOTE: this config file is not used by pytest locally.
+# See comment in mypy.ini.dev for explanation.
+
+# WARNING: when changing this file, consider doing the same with mypy.ini.dev
+
 [mypy]
 allow_redefinition = True
 check_untyped_defs = True