Add metric producers to meter_provider configuration

[dashpole]

Part of https://github.com/open-telemetry/opentelemetry-specification/issues/4015

Metric producers are registered to metric readers, so i've nested it under the periodic and manual readers.

@gouthamve @jack-berg

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• :white_check_mark: login: dashpole / name: David Ashpole (d472dc45786b386db976f127c6b9348d1647cfcf, 9fb79e57c995a12350364ac255bed1e6b9f84494, 70f2ef12652b88131d6bdebf7a04dd8eb5c51de2, 2e05e2765c458bbf0a47a7f0ad93e23c4b99517c)

[codeboten]

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