Add testcore, testoptional deps to pyproject.toml

- To facilitate CI testing with minimal possible set of dependencies.
- Refactor pandas/altair tests to only run when deps installed
- TODO(in this change or future): update CI

pyproject.toml

@@ -92,6 +92,23 @@ dev = [
     "furo==2023.5.20"
 ]
 
+testcore = [
+    "click < 8.1.4",  # https://github.com/pallets/click/issues/2558,
+    # for server testing
+    "httpx~=0.26.0",
+    "pytest~=7.4.0",
+    "pytest-codecov~=0.5.1"
+]
+
+testoptional = [
+    # For testing mo.ui.chart
+    "pandas>=1.3.0",
+    "pandas-stubs>=1.3.0",
+    # polars 0.19.13 requires building maturn from source, but we don't
+    # have the rust toolchain installed on CI
+    "polars==0.19.12",
+]
+
 [project.urls]
 homepage = "https://github.com/marimo-team/marimo"