Update min/max values for lifecycle settings

It doesn't make sense to allow setting these to negative values, so lets
help the user out by refusing to do so if they try.

But leave `-1` as an allowed value for the "discard" option so users can
have "freeze" enabled but turn the discard state off.

Remove the mention of -1 from the freeze setting since we don't allow
that anymore.

qutebrowser/config/configdata.yml

@@ -369,17 +369,21 @@ qt.chromium.use_recommended_page_lifecycle_state:
   # yamllint enable rule:line-length
 
 qt.chromium.lifecycle_state_freeze_delay:
-  type: Int
+  type:
+    name: Int
+    minval: 0
+    maxval: maxint
   default: 0
   backend: QtWebEngine
   desc: >-
     The amount of time (in milliseconds) to wait before transitioning a page to
     the frozen lifecycle state.
 
-    Set to -1 to disable this state (will also disable the discard state).
-
 qt.chromium.lifecycle_state_discard_delay:
-  type: Int
+  type:
+    name: Int
+    minval: -1
+    maxval: maxint
   default: 0
   backend: QtWebEngine
   desc: >-

tests/unit/browser/webengine/test_webenginetab.py

@@ -352,9 +352,9 @@ class TestPageLifecycle:
         """For negative delay values, the timer shouldn't be scheduled."""
         self.set_config(
             config_stub,
-            freeze_delay=-1,
+            discard_delay=-1,
         )
-        webengine_tab._on_recommended_state_changed(QWebEnginePage.LifecycleState.Frozen)
+        webengine_tab._on_recommended_state_changed(QWebEnginePage.LifecycleState.Discarded)
         assert not webengine_tab._lifecycle_timer.isActive()
 
     def test_pinned_tabs_untouched(