[Exporter.Prometheus] Add TargetInfoEnabled option

[martincostello]

Fixes #7158

Changes

Add new TargetInfoEnabled option that allows a user to opt-out of target_info metrics being written to the scrape response.

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 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.19%. Comparing base (f830613) to head (25ed7e7).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...ometheus.AspNetCore/PrometheusAspNetCoreOptions.cs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7438      +/-   ##
==========================================
+ Coverage   90.17%   90.19%   +0.01%     
==========================================
  Files         285      279       -6     
  Lines       15336    14813     -523     
==========================================
- Hits        13830    13361     -469     
+ Misses       1506     1452      -54     

Flag	Coverage Δ
unittests-PowerShellScripts	?
unittests-Project-Experimental	90.04% <87.50%> (-0.10%)	⬇️
unittests-Project-Stable	90.09% <87.50%> (-0.06%)	⬇️
unittests-UnstableCoreLibraries-Experimental	49.68% <87.50%> (-0.01%)	⬇️

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	90.37% <100.00%> (+0.02%)	⬆️
...HttpListener/Internal/Shared/PrometheusExporter.cs	100.00% <100.00%> (ø)
...tener/Internal/Shared/PrometheusExporterOptions.cs	100.00% <100.00%> (ø)
...theusHttpListenerMeterProviderBuilderExtensions.cs	82.35% <100.00%> (+0.53%)	⬆️
...heus.HttpListener/PrometheusHttpListenerOptions.cs	100.00% <100.00%> (ø)
...ometheus.AspNetCore/PrometheusAspNetCoreOptions.cs	50.00% <50.00%> (ø)

... and 12 files with indirect coverage changes

[Copilot]

Pull request overview

This PR adds a configurable TargetInfoEnabled option to the Prometheus exporters (HttpListener and ASP.NET Core) so users can opt out of emitting the target_info metric in scrape responses, aligning with the OpenTelemetry Prometheus exporter spec guidance.

Changes:

• Add TargetInfoEnabled to PrometheusHttpListenerOptions and PrometheusAspNetCoreOptions (default true) and track the new public APIs.
• Wire the option through the exporter pipeline and conditionally skip writing target_info during serialization.
• Add/extend integration tests with snapshots covering both enabled and disabled behaviors, and document the new option.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/snapshots/PrometheusSerializer.RunWithTargetInfoEnabledConfigured_targetInfoEnabled=True.verified.text	New snapshot verifying target_info is present when enabled.
test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/snapshots/PrometheusSerializer.RunWithTargetInfoEnabledConfigured_targetInfoEnabled=False.verified.text	New snapshot verifying target_info is omitted when disabled.
test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/snapshots/PrometheusSerializer.RunHttpServerWithTargetInfoEnabledConfigured_targetInfoEnabled=True.verified.text	New snapshot for HttpListener integration path with target_info enabled.
test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/snapshots/PrometheusSerializer.RunHttpServerWithTargetInfoEnabledConfigured_targetInfoEnabled=False.verified.text	New snapshot for HttpListener integration path with target_info disabled.
test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs	Adds theory test to validate HttpListener option toggling end-to-end.
test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs	Adds theory test to validate ASP.NET Core middleware option toggling end-to-end.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/README.md	Documents TargetInfoEnabled and adds it to the configuration property list.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerOptions.cs	Introduces public TargetInfoEnabled option with default true.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerMeterProviderBuilderExtensions.cs	Propagates TargetInfoEnabled into exporter options used by the metric reader.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusExporterOptions.cs	Adds TargetInfoEnabled to shared exporter options (default true).
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusExporter.cs	Stores TargetInfoEnabled on the exporter instance for downstream use.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusCollectionManager.cs	Conditionally writes target_info based on the new option.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md	Adds Unreleased entry describing the new option.
src/OpenTelemetry.Exporter.Prometheus.HttpListener/.publicApi/PublicAPI.Unshipped.txt	Tracks the new public TargetInfoEnabled API on PrometheusHttpListenerOptions.
src/OpenTelemetry.Exporter.Prometheus.AspNetCore/README.md	Documents TargetInfoEnabled for the ASP.NET Core exporter options.
src/OpenTelemetry.Exporter.Prometheus.AspNetCore/PrometheusAspNetCoreOptions.cs	Introduces public TargetInfoEnabled option (backed by shared exporter options).
src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md	Adds Unreleased entry describing the new option.
src/OpenTelemetry.Exporter.Prometheus.AspNetCore/.publicApi/PublicAPI.Unshipped.txt	Tracks the new public TargetInfoEnabled API on PrometheusAspNetCoreOptions.

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