remove prom pull based exporter

[ttys3]

opentelemetry-rust

ref open-telemetry/opentelemetry-rust#1719

these features maybe removed:

1. Metrics SDK's View feature. Would need to gather feedback about the common use cases where Views are needed. My own experience is that, it is used most frequently to provide custom Histogram bounds. Before removing View feature, the ability to provide custom bounds will be provided at the API level. The main reason why it is removed from initial release is to keep scope manageable. Views bring a whole lot of new complexities and additional test requirements.

2. Prometheus/Pull Exporter.

and

open-telemetry/opentelemetry-rust#1957 (review)

most likely the upcoming changes will not support pull based exporting at all

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Prometheus OTLP Ingestion GA

https://prometheus.io/blog/2024/03/14/commitment-to-opentelemetry/#otlp-ingestion-ga

In Prometheus v2.47.0, released on 6th September 2023, we added experimental support for OTLP ingestion in Prometheus. We’re constantly improving this and we plan to add support for staleness and make it a stable feature. We will also mark our support for out-of-order ingestion as stable. This involves also GA-ing our support for native / exponential histograms.

https://prometheus.io/docs/prometheus/latest/feature_flags/#otlp-receiver