Add remote write protocol 2.0 support

[pstibrany]

What should we do?

Prometheus added remote write protocol 2.0 experimental support in v2.54.0 (released on 2024-08-09). We should add the support in Mimir too.

Spec: https://prometheus.io/docs/specs/remote_write_spec_2_0/

How will we do it (roughly)?

• Add remote write 2.0 support in Mimir distributors
• Backport all (applicable) optimizations we did to remote write 1.0 (un)marshalling
• Compare performance between remote write 1.0 and 2.0
• Allow to enable 2.0 support on a per-tenant basis

Out of the scope of this work:

• Change data format between distributors and ingesters / Kafka (keep using protocol 1.0 format). This should be a follow up deliverable.

[pstibrany]

Duplicate of #9072