[extension/opamp] Make the polling interval configurable for HTTP client

[matej-g]

Component(s)

extension/opamp

Is your feature request related to a problem? Please describe.

Currently, the OpAMP extension's HTTP client is using the default 30 second interval and it cannot be configured. I would like to use a bigger interval for polling. The OpAMP specification states that this should be configurable on the client, as well (see https://opentelemetry.io/docs/specs/opamp/#plain-http-transport).

Describe the solution you'd like

Add a configuration option for polling interval and apply it to the HTTP client.

Describe alternatives you've considered

No response

Additional context

No response

[github-actions]

Pinging code owners:

• extension/opamp: @portertech @evan-bradley @tigrannajaryan @BinaryFissionGames

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[matej-g]

Assuming there are no objections, I prepared a PR for this - #34811. Thanks.