Allow overriding http.(client/server).request.duration buckets via environment variables to control cardinality

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

By default, the http.(client/server).request.duration metrics has 14 defined buckets, as specified in the SemConv for this metric. While this is correct, it would be really useful if it were possible to define the buckets via an environment variable to reduce cardinality in our metrics.
This would allow us to continue using the java-agent.jar out-of-the-box without having to add any additional programmatic configuration. By supporting environment variables, we can maintain a purely declarative setup, which is more infrastructure-as-code friendly and avoids the need for custom SDK extensions or manual code changes.

Describe the solution you'd like

I would like to see a new configuration option, for example, an environment variable like OTEL_HTTP_METRICS_BUCKETS that allows users to provide a comma-separated list of values

Describe alternatives you've considered

No response

Additional context

No response

Tip

_{React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it. Learn more here.}

Start by locating the HTTP client and server request.duration instrumentation, its bucket configuration, and existing environment-variable parsing tests. Verify how a comma-separated OTEL_HTTP_METRICS_BUCKETS value should be interpreted, then add coverage for both instrumentations and confirm that the configured buckets replace the defaults.