feat: add metrics query API (#1394)

# What does this PR do?
Adds the API to query metrics from telemetry.

## Test Plan
llama stack run ~/.llama/distributions/fireworks/fireworks-run.yaml

---------

Co-authored-by: Ashwin Bharambe <ashwin.bharambe@gmail.com>

docs/_static/llama-stack-spec.yaml

@@ -2397,6 +2397,40 @@ paths:
             schema:
               $ref: '#/components/schemas/QueryChunksRequest'
         required: true
+  /v1/telemetry/metrics/{metric_name}:
+    post:
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/QueryMetricsResponse'
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - Telemetry
+      description: ''
+      parameters:
+        - name: metric_name
+          in: path
+          required: true
+          schema:
+            type: string
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/QueryMetricsRequest'
+        required: true
   /v1/telemetry/spans:
     post:
       responses:
@@ -7762,6 +7796,104 @@ components:
         - chunks
         - scores
       title: QueryChunksResponse
+    QueryMetricsRequest:
+      type: object
+      properties:
+        start_time:
+          type: integer
+        end_time:
+          type: integer
+        granularity:
+          type: string
+        query_type:
+          type: string
+          enum:
+            - range
+            - instant
+          title: MetricQueryType
+        label_matchers:
+          type: array
+          items:
+            type: object
+            properties:
+              name:
+                type: string
+              value:
+                type: string
+              operator:
+                type: string
+                enum:
+                  - '='
+                  - '!='
+                  - =~
+                  - '!~'
+                title: MetricLabelOperator
+                default: '='
+            additionalProperties: false
+            required:
+              - name
+              - value
+              - operator
+            title: MetricLabelMatcher
+      additionalProperties: false
+      required:
+        - start_time
+        - query_type
+      title: QueryMetricsRequest
+    MetricDataPoint:
+      type: object
+      properties:
+        timestamp:
+          type: integer
+        value:
+          type: number
+      additionalProperties: false
+      required:
+        - timestamp
+        - value
+      title: MetricDataPoint
+    MetricLabel:
+      type: object
+      properties:
+        name:
+          type: string
+        value:
+          type: string
+      additionalProperties: false
+      required:
+        - name
+        - value
+      title: MetricLabel
+    MetricSeries:
+      type: object
+      properties:
+        metric:
+          type: string
+        labels:
+          type: array
+          items:
+            $ref: '#/components/schemas/MetricLabel'
+        values:
+          type: array
+          items:
+            $ref: '#/components/schemas/MetricDataPoint'
+      additionalProperties: false
+      required:
+        - metric
+        - labels
+        - values
+      title: MetricSeries
+    QueryMetricsResponse:
+      type: object
+      properties:
+        data:
+          type: array
+          items:
+            $ref: '#/components/schemas/MetricSeries'
+      additionalProperties: false
+      required:
+        - data
+      title: QueryMetricsResponse
     QueryCondition:
       type: object
       properties: