Metrics API - Move to builder pattern for creating Meters

[cijothomas]

Related to #1527, but for Metrics
This is part of Metrics API, and hence must be done by Metrics API RC.

[stormshield-fabs]

This was made a bit more complicated with the object-safety requirement on MeterProvider added in #2112

The problem is mostly about ergonomics because we probably can't have an API similar to the other signals.

I don't think we want to re-introduce ObjectSafeMeterProvider, since we would not be able to forward the builder method anyway, but a solution could be to have a "standalone" MeterBuilder (without the MeterProvider::meter_builder method).

[cijothomas]

@utpilla can you help with this?

ALso https://github.com/open-telemetry/opentelemetry-rust/blob/main/opentelemetry/src/common.rs#L413 is something we want to remove from opentelemetry crate. (okay to be in sdk crate)