feat: Improve Report API performance (#9476)

- Re-write the methods for clarity
- Remove the dependency on the ReportHelper class.
- Remove n+1 queries in the average metric time series data.

app/helpers/timezone_helper.rb

@@ -0,0 +1,19 @@
+module TimezoneHelper
+  # ActiveSupport TimeZone is not aware of the current time, so ActiveSupport::Timezone[offset]
+  # would return the timezone without considering day light savings. To get the correct timezone,
+  # this method uses zone.now.utc_offset for comparison as referenced in the issues below
+  #
+  # https://github.com/rails/rails/pull/22243
+  # https://github.com/rails/rails/issues/21501
+  # https://github.com/rails/rails/issues/7297
+  def timezone_name_from_offset(offset)
+    return 'UTC' if offset.blank?
+
+    offset_in_seconds = offset.to_f * 3600
+    matching_zone = ActiveSupport::TimeZone.all.find do |zone|
+      zone.now.utc_offset == offset_in_seconds
+    end
+
+    return matching_zone.name if matching_zone
+  end
+end