Add uniqueness check to "Create project" command (#5100)

* Add failing playwright test

* Make create generate a unique name if the given one collides

* Add a new consolidated getUniqueProjectName function with tests

* Use getUniqueProjectName

* Replace "New project" button text with "Create project"
cc @pierremtb

* Extend the e2e test to show the incrementing behavior
cc @lf94

src/components/CommandBar/CommandArgOptionInput.tsx

@@ -134,6 +134,7 @@ function CommandArgOptionInput({
           </label>
           <Combobox.Input
             id="option-input"
+            data-testid="cmd-bar-arg-value"
             ref={inputRef}
             onChange={(event) =>
               !event.target.disabled && setQuery(event.target.value)