* develop:
  Widget test cleanup (streamlit#3286)
  pin click to < 8.0 (streamlit#3256)
  Up version to 0.82.0
  Update change log

Implements `clear_on_submit`, a new optional parameter for st.form. When a form has this flag, it means that the frontend "resets" all the form's widgets when the form is submitted.

CustomComponents are _not_ currently affected by this flag (this is by design - properly handling this would require a CustomComponents API update, and all widget-like components in the wild would need updating. So we're punting on it for now).

- `FormsManager` is now folded into `WidgetStateManager`.
- When a form is submitted, `WidgetStateManager` emits a signal. All widgets in the form respond to this signal by resetting their values locally and committing those values back to the WidgetStateManager.
- This resetting only happens on the frontend - the server doesn't know that values have been reset (this is by design).
- `FormClearHelper` is a utility class that implements a `useEffect`-like pattern for subscribing to the `formCleared` events. (None of our widgets are currently implemented using React hooks, so this is a workaround for easily and correctly composing that behavior into each widget.)
- Each widget has a new test for `clearOnSubmit` behavior.
- `st.form_submit_button` now takes an optional "help" parameter.

(Contains changes from #3286, which should be reviewed first)

# By Ken McGrady (19) and others
# Via GitHub (9) and others
* develop: (96 commits)
  st.form: clear_on_submit (streamlit#3287)
  Init test variables in beforeEach
  Init test variables in beforeEach
  Add database tutorials to docs (streamlit#3272)
  update contact email to support (streamlit#3282)
  Better typing
  Remove dummy script
  Add testing and some comments
  Fix the bug, don't love the solution
  Improve test name
  Add script for testing
  Fix test after merge
  Make sure selected options aren't visible in the dropdown
  Widget test cleanup (streamlit#3286)
  Add test for the fuzzy filter
  Import filter function from another component
  Remove tag from PR template (streamlit#3284)
  Add test req version bound for TF to fix tests (streamlit#3266)
  pin click to < 8.0 (streamlit#3256)
  Up version to 0.82.0
  ...

# Conflicts:
#	frontend/src/components/shared/Dropdown/Selectbox.test.tsx