Override mappings for context from the shim

[harsimar]

Related to: microsoft/ApplicationInsights-dotnet#3137
This PR is to ensure that context set from the shim shows up as tags (not custom dimensions) in most telemetry types (not including metrics)

[Copilot]

Pull request overview

This PR extends the Azure Monitor OpenTelemetry Exporter to treat additional Application Insights shim context values as envelope tags (instead of custom dimensions), aiming for consistent behavior across telemetry types (including metrics), and adds an environment-variable override for application/component version.

Changes:

• Adds support for overriding ai.application.ver via APPLICATIONINSIGHTS_COMPONENT_VERSION.
• Introduces new shim context tag attribute constants and mapping paths (Activity tags, log attributes, and metric tags) to populate TelemetryItem.Tags.
• Updates/extends E2E and unit tests to validate the new context-tag-to-envelope-tag behavior.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Customizations/Models/TelemetryItem.cs	Adds environment variable override for component version; copies/mapping of additional context tags into envelope tags.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/ActivityTagsProcessor.cs	Extends the set of recognized Activity semantic attributes for shim context tags.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs	Extends log attribute extraction into LogContextInfo for mapping into envelope tags.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogContextInfo.cs	Adds new extracted context fields for logs.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/MetricHelper.cs	Adds metric-tag-to-envelope-tag mapping hook for metrics.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/SemanticConventions.cs	Adds constants for shim context attributes.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/SchemaConstants.cs	Adds max-length constants for newly mapped envelope tags.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/Platform/EnvironmentVariableConstants.cs	Adds APPLICATIONINSIGHTS_COMPONENT_VERSION constant and includes it in override-related environment variable sets.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/**/TelemetryItemTests.cs	Adds unit test for APPLICATIONINSIGHTS_COMPONENT_VERSION override.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/**/LogsHelperTests.cs	Removes user-agent log-context test coverage and updates combined-context tests accordingly.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/**/E2ETelemetryItemValidation/TracesTests.cs	Adds E2E validation that shim context attributes map to envelope tags and not custom dimensions for traces.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/**/E2ETelemetryItemValidation/LogsTests.cs	Adds E2E validation that shim context attributes map to envelope tags and not custom dimensions for logs.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/**/E2ETelemetryItemValidation/MetricsTests.cs	Adds an Internals using (currently unused).

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