Refactor rate limit helper to track time in seconds (#113898)

* Refactor rate limit helper to track time in seconds

Currently we created datetime and timedelta objects to enforce the
rate limit. When the rate limit was being hit hard, this got expensive.

We now use floats everywhere instead as they are much cheaper which
is important when we are running up against a rate limit, which is
by definition a hot path

The rate limit helper is currently only used for templates and
we do not have any code in the code base that directly passes
in a rate limit so the impact to custom components is expected
to be negligible if any

* misesd two

homeassistant/helpers/event.py

@@ -141,7 +141,7 @@ class TrackTemplate:
 
     template: Template
     variables: TemplateVarsType
-    rate_limit: timedelta | None = None
+    rate_limit: float | None = None
 
 
 @dataclass(slots=True)
@@ -1077,7 +1077,7 @@ class TrackTemplateResultInfo:
     def _render_template_if_ready(
         self,
         track_template_: TrackTemplate,
-        now: datetime,
+        now: float,
         event: Event[EventStateChangedData] | None,
     ) -> bool | TrackTemplateResult:
         """Re-render the template if conditions match.
@@ -1185,7 +1185,7 @@ class TrackTemplateResultInfo:
         """
         updates: list[TrackTemplateResult] = []
         info_changed = False
-        now = event.time_fired if not replayed and event else dt_util.utcnow()
+        now = event.time_fired_timestamp if not replayed and event else time.time()
 
         block_updates = False
         super_template = self._track_templates[0] if self._has_super_template else None
@@ -1927,7 +1927,7 @@ def _rate_limit_for_event(
     event: Event[EventStateChangedData],
     info: RenderInfo,
     track_template_: TrackTemplate,
-) -> timedelta | None:
+) -> float | None:
     """Determine the rate limit for an event."""
     # Specifically referenced entities are excluded
     # from the rate limit
@@ -1937,7 +1937,7 @@ def _rate_limit_for_event(
     if track_template_.rate_limit is not None:
         return track_template_.rate_limit
 
-    rate_limit: timedelta | None = info.rate_limit
+    rate_limit: float | None = info.rate_limit
     return rate_limit