test: replace testbench tests with playwright (Java and Ts)

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Unit Test Results

10 tests  ±0   10 ✔️ ±0   10s ⏱️ -5s
  2 suites ±0     0 💤 ±0 
  2 files   ±0     0 ❌ ±0 

Results for commit 81fd1a0. ± Comparison against base commit 3518116.

This pull request removes 6 and adds 6 tests. Note that renamed tests count towards both.

org.vaadin.example.FlowViewIT ‑ testEnterShowsHelloUserNotificationWhenUserIsNotEmpty
org.vaadin.example.HillaViewIT ‑ clickingButtonShowsNotification
org.vaadin.example.HillaViewIT ‑ clickingButtonTwiceShowsTwoNotifications
org.vaadin.example.HillaViewIT ‑ testClickButtonShowsHelloAnonymousUserNotificationWhenUserNameIsEmpty
org.vaadin.example.HillaViewIT ‑ testClickButtonShowsHelloUserNotificationWhenUserIsNotEmpty
org.vaadin.example.HillaViewIT ‑ testEnterShowsHelloUserNotificationWhenUserIsNotEmpty

hilla.spec.ts ‑ click button shows Hello Anonymous User notification when user name is empty
hilla.spec.ts ‑ click button shows Hello User notification when user is not empty
hilla.spec.ts ‑ clicking button shows notification
hilla.spec.ts ‑ clicking button twice shows two notifications
hilla.spec.ts ‑ user enters name and clicks button
org.vaadin.example.FlowViewIT ‑ userEntersNameAndClicksButton