This adds the [unparam](https://github.com/mvdan/unparam) linter.
Co-authored-by: Sam Xie <sam@samxie.me>
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>
Add the `x` package to handle experimental feature flagging within the
go.opentelemetry.io/otel/sdk module. Currently this only supports
enabling experimental resource semantic conventions.
Resolve#5436
cc @pyohannes
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Co-authored-by: Sam Xie <sam@samxie.me>