Metrics reader supports configuring aggregation and temporality

[kaylareopelle]

The metrics Reader implementation should support configuring the default aggregation and the default temporality on the basis of instrument kind. There are two lines on the spec compliance matrix about this.

This may be the relevant spec: https://opentelemetry.io/docs/specs/otel/metrics/sdk/#metricreader

Our aggregation classes set the temporality and it can be configured using an environment variable, OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE

Our instruments have a default temporality and don't have a public-facing API to change their aggregation. We should look at the configuration options for aggregation and temporality and see if they are compliant. If they are not, update the SDK to make it compliant.

[github-actions]

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