feat(exporters/prometheus): add explicit option to set naming scheme

[juliusmh]

No description provided.

[linux-foundation-easycla]

• ❌ - login: @juliusmh / name: Julius Hinze . The commit (32a3e65) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[dmathieu]

cc @dashpole

I'm not sure this can work. NameValidationScheme is a value that the prometheus/model package uses to for its naming scheme globally. We can't configure a global config locally unless the library allows it.
See https://pkg.go.dev/github.com/prometheus/common/model#pkg-variables

[dashpole]

We are probably going to switch to "translation modes" to match the Prometheus server's OTLP endpoint configuration: open-telemetry/opentelemetry-specification#4533