feat: divide dependencies in pyproject.toml into core and optional

A previous PR in this branch removed `test_requirements/requirements_core.txt`
and `test_requirements/requirements_optional.txt`. @emilylk pointed out that
these files are used in Circle CI to set up a minimal environment for running
`tests/test_core/*` and then a larger environment for running the other tests
(the idea being to prevent extra dependencies from sneaking into plotly.py).
This PR divides dependencies into `dev_core` and `dev_optional` with `dev`
essentially aliasing `dev_optional` so that `./.circleci/config.yml` can be
modified to use these for installation.

Author: gvwilson

pyproject.toml

@@ -47,7 +47,14 @@ dependencies = [
 [project.optional-dependencies]
 express = ["numpy"]
 kaleido = ["kaleido==1.0.0rc15"]
-dev = [
+dev_core = [
+    "pytest",
+    "requests"
+]
+dev_optional = [
+    # all core dependencies
+    "plotly[dev_core]",
+
     # pin precise version of ruff to prevent accidental reformatting in case its defaults are updated
     "ruff==0.11.12",
 
@@ -68,15 +75,16 @@ dev = [
     "polars",
     "pyarrow",
     "pyshp",
-    "pytest",
     "pytz",
-    "requests",
     "scipy",
     "scikit-image",
     "shapely",
     "statsmodels",
     "xarray"
 ]
+dev = [
+    "plotly[dev_optional]"
+]
 
 [project.scripts]
 plotly_get_chrome = "plotly.io._kaleido:get_chrome"