[otel] add support for more trace sampling strategies

Right now we only support (`parentbased_always_on`). We should support:

- `always_on`
- `always_off`
- `traceidratio`
- `parentbased_always_on`
- `parentbased_always_off`
- `parentbased_traceidratio`

This should be configured with `OTEL_TRACES_SAMPLER` and `OTEL_TRACES_SAMPLER_ARG`.

https://opentelemetry.io/docs/languages/sdk-configuration/general/#otel_traces_sampler