Cleanup on aisle METRICS. Note: See below, this is a breaking change

1. Fleshed out MetricsFrames and broke it into a proper set of types
2. Add model_name as a property to the AIService so that it can be
   automatically included in metrics and also remove that
   overhead from all the various services themselves

Breaking change!

Because of the types improvements, the MetricsFrame type has
changed. Each frame will have a list of metrics simlilar to before
except each item in the list will only contain one type of metric:
"ttfb", "tokens", "characters", or "processing". Previously these
fields would be in every entry but set to None if they didn't apply.

While this changes internal handling of the MetricsFrame, it does NOT
break the RTVI/daily messaging of metrics. That format remains the same.

Also. Remember to use model_name for accessing a service's current
model and set_model_name for setting it.

src/pipecat/frames/frames.py

@@ -4,11 +4,12 @@
 # SPDX-License-Identifier: BSD 2-Clause License
 #
 
-from typing import Any, List, Mapping, Optional, Tuple
+from typing import Any, List, Optional, Tuple
 
 from dataclasses import dataclass, field
 
 from pipecat.clocks.base_clock import BaseClock
+from pipecat.metrics.metrics import MetricsData
 from pipecat.transcriptions.language import Language
 from pipecat.utils.time import nanoseconds_to_str
 from pipecat.utils.utils import obj_count, obj_id
@@ -333,10 +334,8 @@ class BotInterruptionFrame(SystemFrame):
 class MetricsFrame(SystemFrame):
     """Emitted by processor that can compute metrics like latencies.
     """
-    ttfb: List[Mapping[str, Any]] | None = None
-    processing: List[Mapping[str, Any]] | None = None
-    tokens: List[Mapping[str, Any]] | None = None
-    characters: List[Mapping[str, Any]] | None = None
+    data: List[MetricsData]
+
 
 #
 # Control frames