Migrate st_session_state to playwright (streamlit#8918)

## Describe your changes
- title
## GitHub Issue Link (if applicable)

## Testing Plan

- Explanation of why no additional tests are needed
- Unit Tests (JS and/or Python)
- E2E Tests
- Any manual testing needed?

---

**Contribution License Agreement**

By submitting this pull request you agree that all contributions to this
project are made under the Apache 2.0 license.

e2e_playwright/st_session_state.py

@@ -31,3 +31,30 @@ def on_checkbox_change(changed_checkbox_number):
     st.checkbox(
         label="Checkbox2", key="checkbox2", on_change=on_checkbox_change, args=(2,)
     )
+
+    if "initialized" not in st.session_state:
+        st.session_state["item_counter"] = 0
+        st.session_state.attr_counter = 0
+
+        st.session_state.initialized = True
+
+    if st.button("inc_item_counter"):
+        st.session_state["item_counter"] += 1
+
+    if st.button("inc_attr_counter"):
+        st.session_state.attr_counter += 1
+
+    if st.button("del_item_counter"):
+        del st.session_state["item_counter"]
+
+    if st.button("del_attr_counter"):
+        del st.session_state.attr_counter
+
+    if "item_counter" in st.session_state:
+        st.write(f"item_counter: {st.session_state['item_counter']}")
+
+    if "attr_counter" in st.session_state:
+        st.write(f"attr_counter: {st.session_state.attr_counter}")
+
+    st.write(f"len(st.session_state): {len(st.session_state)}")
+    st.write(st.session_state)

e2e_playwright/st_session_state_test.py

@@ -14,7 +14,7 @@
 
 from playwright.sync_api import Page, expect
 
-from e2e_playwright.shared.app_utils import click_checkbox, get_checkbox
+from e2e_playwright.shared.app_utils import click_button, click_checkbox, get_checkbox
 
 
 def test_checking_checkbox_unchecks_other(app: Page):
@@ -29,3 +29,52 @@ def test_checking_checkbox_unchecks_other(app: Page):
 
     expect(first_checkbox.locator("input")).to_have_attribute("aria-checked", "false")
     expect(second_checkbox.locator("input")).to_have_attribute("aria-checked", "true")
+
+
+def test_has_correct_starting_values(app: Page):
+    expect(app.get_by_text("item_counter: 0")).to_have_count(1)
+    expect(app.get_by_text("attr_counter: 0")).to_have_count(1)
+    expect(app.get_by_text("len(st.session_state): 5")).to_have_count(1)
+    expect(app.get_by_test_id("stJson")).to_be_visible()
+
+
+def test_can_do_CRUD_for_session_state_items(app: Page):
+    expect(app.get_by_text("item_counter: 0")).to_have_count(1)
+    expect(app.get_by_text("attr_counter: 0")).to_have_count(1)
+
+    click_button(app, "inc_item_counter")
+
+    expect(app.get_by_text("item_counter: 1")).to_have_count(1)
+    expect(app.get_by_text("attr_counter: 0")).to_have_count(1)
+
+    click_button(app, "inc_item_counter")
+
+    expect(app.get_by_text("item_counter: 2")).to_have_count(1)
+    expect(app.get_by_text("attr_counter: 0")).to_have_count(1)
+
+    click_button(app, "del_item_counter")
+
+    expect(app.get_by_text("item_counter: 2")).to_have_count(0)
+    expect(app.get_by_text("attr_counter: 0")).to_have_count(1)
+    expect(app.get_by_text("len(st.session_state): 4")).to_have_count(1)
+
+
+def test_can_do_CRUD_for_session_state_attributes(app: Page):
+    expect(app.get_by_text("item_counter: 0")).to_have_count(1)
+    expect(app.get_by_text("attr_counter: 0")).to_have_count(1)
+
+    click_button(app, "inc_attr_counter")
+
+    expect(app.get_by_text("item_counter: 0")).to_have_count(1)
+    expect(app.get_by_text("attr_counter: 1")).to_have_count(1)
+
+    click_button(app, "inc_attr_counter")
+
+    expect(app.get_by_text("item_counter: 0")).to_have_count(1)
+    expect(app.get_by_text("attr_counter: 2")).to_have_count(1)
+
+    click_button(app, "del_attr_counter")
+
+    expect(app.get_by_text("item_counter: 0")).to_have_count(1)
+    expect(app.get_by_text("attr_counter: 2")).to_have_count(0)
+    expect(app.get_by_text("len(st.session_state): 4")).to_have_count(1)