Entity cache: convert spans and metrics to the new format

[Geal]

This converts the entity cache metrics to the new metric format and using the custom telemetry stack.

Here is an example of configuration:

telemetry:
  instrumentation:
    instruments:
      default_requirement_level: none
      cache:
        apollo.router.operations.entity.cache:
          attributes:
            entity.type: true
            subgraph.name:
              subgraph_name: true
            supergraph.operation.name:
              supergraph_operation_name: string
      subgraph:
        only_cache_hit_on_subgraph_products:
          type: counter
          value:
            cache: hit
          unit: hit
          description: counter of subgraph request cache hit on subgraph products
          condition:
            all:
            - eq:
              - subgraph_name: true
              - products
            - gt:
              - cache: hit
              - 0
          attributes:
            subgraph.name: true
            supergraph.operation.name:
              supergraph_operation_name: string

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Checklist

Complete the checklist (and note appropriate exceptions) before the PR is marked ready-for-review.

• Changes are compatible¹
• Documentation² completed
• Performance impact assessed and acceptable
• Tests added and passing³
  • Unit Tests
  • Integration Tests
  • Manual Tests

Exceptions

Note any exceptions here

Notes

Footnotes

1. It may be appropriate to bring upcoming changes to the attention of other (impacted) groups. Please endeavour to do this before seeking PR approval. The mechanism for doing this will vary considerably, so use your judgement as to how and when to do this. ↩

2. Configuration is an important part of many changes. Where applicable please try to document configuration examples. ↩

3. Tick whichever testing boxes are applicable. If you are adding Manual Tests, please document the manual testing (extensively) in the Exceptions. ↩