ENH: Improved typing and docs for scatter plot (shap#3811)

* WIP type hints for scatter

* Simplify axes handling

* Improve docs

* Fixup test plot dims

* Refactor out x_jitter

* Split out histogram

* Return axes if show=False

* Fixup typo

* Docs formatting fixes

* apply suggestion

Co-authored-by: Jeremy Goh <30731072+thatlittleboy@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Jeremy Goh <30731072+thatlittleboy@users.noreply.github.com>

* Updates from review

* Further PR suggestions

* Simplify the use of `ind` variable

* Better docs for `overlay` param

---------

Co-authored-by: Jeremy Goh <30731072+thatlittleboy@users.noreply.github.com>

.gitignore

@@ -36,3 +36,4 @@ __pycache__
 /tests/mnist_data
 catboost_info
 node_modules
+mpl-results

pyproject.toml

@@ -141,7 +141,6 @@ module = [
   "shap.plots._benchmark",
   "shap.plots._force_matplotlib",
   "shap.plots._force",
-  "shap.plots._scatter.*",
   "shap.plots._text",
   "shap.plots._waterfall",
 ]