Fix cpython.gc metrics to use semantic convention attribute names

[Copilot]

Description

The cpython.gc metrics (collections, collected_objects, uncollectable_objects) were using non-namespaced attribute name "generation" with string values, violating semantic conventions which require "cpython.gc.generation" with integer values.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Changes

• Import semantic convention constant: Added CPYTHON_GC_GENERATION from opentelemetry.semconv._incubating.attributes.cpython_attributes
• Updated attribute references in callbacks: Changed hardcoded "generation" to CPYTHON_GC_GENERATION constant in:
  • _get_runtime_gc_collections()
  • _get_runtime_gc_collected_objects()
  • _get_runtime_gc_uncollectable_objects()
• Fixed attribute values: Changed from str(index) to index for proper integer typing (0, 1, 2)
• Updated tests: Modified expectations to match new attribute name and integer values

Before:

self._runtime_gc_collections_labels["generation"] = str(index)  # Wrong: no namespace, string value

After:

self._runtime_gc_collections_labels[CPYTHON_GC_GENERATION] = index  # Correct: "cpython.gc.generation", int value

How Has This Been Tested?

• All 41 existing system metrics tests pass
• Specific gc metrics tests verify correct attribute name and integer values

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

Original prompt

Please look at the following report and open a pr to fix the violations listed there in opentelemetry-instrumentation-system-metrics package that is inside the instrumentation dir. On that instrumentation the name of the attributes are taken from the opentelemetry-semantic-conventions package, so you should grep https://github.com/open-telemetry/opentelemetry-python/tree/main/opentelemetry-semantic-conventions/ to get the variable name referenced in the opentelemetry-instrumentation-system-metrics package.

Here's the report:

Metric cpython.gc.collections counter, {collection}
- [improvement] Metric 'cpython.gc.collections' is not stable; stability = development.
Data point 125
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 0
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')
Data point 11
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 1
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')
Data point 1
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 2
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')

Metric cpython.gc.collected_objects counter, {object}
- [improvement] Metric 'cpython.gc.collected_objects' is not stable; stability = development.
Data point 601
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 0
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')
Data point 78
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 1
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')
Data point 20
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 2
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')

Metric cpython.gc.uncollectable_objects counter, {object}
- [improvement] Metric 'cpython.gc.uncollectable_objects' is not stable; stability = development.
Data point 0
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 0
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')
Data point 0
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 1
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')
Data point 0
- [violation] Required attribute 'cpython.gc.generation' is not present.
generation = 2
- [violation] Attribute 'generation' does not exist in the registry.
- [improvement] Attribute name 'generation' must include a namespace (e.g. '{namespace}.{attribute_key}')

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