[PIP-264] OTel should support pushdown predicate

[asafm]

Overview

Pulsar PIP-264 will introduce a filter to reduce amount of metrics exported, which is especially relevant when number of topics is large (10k - 100k per broker). This filter must be implemented inside OpenTelemetry SDK, otherwise there will be a large penalty of high memory usage, garbage collection and probably CPU, as demonstrated in this draft PR.
The goal here is to modify OTel specifications to include a filter and subsequently implement it in OTel Java SDK.

Parent issue: #21121

Tasks

• 🔄 OTel specifications should have a pushdown predicate
  • Create issue
    • Proposal: Add filter predicate to MetricReader (push-down predicate) open-telemetry/opentelemetry-specification#3324
  • Garner favorable agreement from the community
  • Write the proposal as PR
    • Add predicate to MetricReader and MetricProducer open-telemetry/opentelemetry-specification#3566
  • 🔄 Work on PR to get it approved
• OTel Java should support pushdown predicate
  • Design and approve
  • Write code with tests
  • Get PR approved

[github-actions]

The issue had no activity for 30 days, mark with Stale label.

[asafm]

Still working on the PR to be approved: open-telemetry/opentelemetry-specification#3566
Some progress have been made.

[github-actions]

The issue had no activity for 30 days, mark with Stale label.

[asafm]

Still working. Mainly blocked on a question I have in this PR

[asafm]

Moved the plan into a single page plan here