Modify track calls to not modify the passed in dictionary

[harsimar]

Related to: #3117

[Copilot]

Pull request overview

This PR fixes a breaking change introduced in 3.x pre-releases where Track* methods mutated the caller's properties dictionary, causing System.NotSupportedException when passing immutable dictionary implementations (common in F# with dict/Map) and ArgumentException on repeated calls with the same dictionary instance.

Changes:

• Modified TrackEvent, TrackTrace, and TrackException methods to create internal copies of properties dictionaries before adding framework attributes
• Added comprehensive test coverage for immutable dictionary support and non-mutation guarantees
• Updated breaking changes documentation to describe the fix

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
BASE/src/Microsoft.ApplicationInsights/TelemetryClient.cs	Modified TrackEvent(string, IDictionary), TrackEvent(EventTelemetry), TrackTrace(TraceTelemetry), and TrackException(ExceptionTelemetry) to copy properties before adding internal attributes instead of mutating caller's dictionary
BASE/Test/Microsoft.ApplicationInsights.Test/Microsoft.ApplicationInsights.Tests/TelemetryClientTest.cs	Added comprehensive tests verifying non-mutation behavior, immutable dictionary support (ReadOnlyDictionary), and repeated calls with same dictionary for TrackEvent, TrackTrace, and TrackException methods
BreakingChanges.md	Added documentation section describing the issue in earlier 3.x pre-releases and confirming the fix ensures all Track* methods no longer mutate caller's dictionaries

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