[Exporter.Prometheus] Add translation strategy infra

[martincostello]

Contributes to #7156

Changes

Introduce internal PrometheusTranslationStrategy enum and thread a metric-name suffix-suppression policy from options through to PrometheusMetric.

A follow-up PR will expose the option into the public API and configure how it interacts with the Accept header to determine precedence.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.26%. Comparing base (af56ce6) to head (1cb8907).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
.../Shared/PrometheusTranslationStrategyExtensions.cs	87.50%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7503   +/-   ##
=======================================
  Coverage   90.26%   90.26%           
=======================================
  Files         288      289    +1     
  Lines       15658    15687   +29     
=======================================
+ Hits        14133    14160   +27     
- Misses       1525     1527    +2     

Flag	Coverage Δ
unittests-Project-Experimental	90.17% <94.44%> (-0.16%)	⬇️
unittests-Project-Stable	90.28% <94.44%> (-0.06%)	⬇️
unittests-UnstableCoreLibraries-Experimental	51.10% <94.44%> (+0.08%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ner/Internal/Shared/PrometheusCollectionManager.cs	92.37% <100.00%> (ø)
...HttpListener/Internal/Shared/PrometheusExporter.cs	100.00% <100.00%> (ø)
...tener/Internal/Shared/PrometheusExporterOptions.cs	100.00% <100.00%> (ø)
...s.HttpListener/Internal/Shared/PrometheusMetric.cs	99.59% <100.00%> (+0.01%)	⬆️
.../Shared/PrometheusTranslationStrategyExtensions.cs	87.50% <87.50%> (ø)

[Copilot]

Pull request overview

Introduces internal infrastructure for Prometheus translation strategy selection and threads a “metric name suffix suppression” policy from exporter options into PrometheusMetric, enabling future configuration of name translation behavior.

Changes:

• Add internal PrometheusTranslationStrategy enum plus extension helpers for mapping strategy → escaping scheme and suffix behavior.
• Plumb TranslationStrategy from PrometheusExporterOptions → PrometheusExporter → PrometheusCollectionManager → PrometheusMetric to control whether unit/_total suffixes are appended.
• Add/extend unit tests to validate suffix-suppression behavior and strategy mappings.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusTranslationStrategyTests.cs	Adds unit tests for strategy defaults and mapping behavior.
test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusMetricTests.cs	Adds test coverage for appendSuffixes: false behavior across escaping schemes and counter naming.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusTranslationStrategyExtensions.cs	Adds internal mapping helpers from translation strategy to escaping/suffix behavior.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusTranslationStrategy.cs	Introduces the internal translation strategy enum.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusMetric.cs	Implements suffix suppression in name generation and threads appendSuffixes through all name builders.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusExporterOptions.cs	Adds TranslationStrategy option with default.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusExporter.cs	Stores the configured strategy and exposes AppendSuffixes derived from it.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusCollectionManager.cs	Passes exporter suffix policy into PrometheusMetric.Create.

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