chore: Add integration tests for tracing

[tustanivsky]

The existing unit tests for tracing had two issues:

• Subsystem re-initialization: Both SentrySubsystem.spec.cpp (transaction lifecycle) and SentryTraceSampling.spec.cpp (custom trace sampler) called Close() + InitializeWithSettings() in BeforeEach, which caused flakiness and interfered with other tests in the automation suite.
• No end-to-end validation: The tests only verified local API behavior (e.g. IsFinished() returns true after Finish()). They never validated that the transaction and its spans actually reached Sentry with the expected data.

Key changes:

• Add tracing-capture test scenario to the sample app that starts a transaction with child and grandchild spans, sets and
  removes tags and data on both, and outputs the trace ID for lookup
• Add CppTraceSampler to the sample app that accepts transactions matching the test name and discards all others,
  exercising the custom TracesSampler pipeline
• Use StartTransactionWithContextAndOptions with custom sampling context to cover the full transaction creation path
• Add tracing integration tests for Desktop (Windows/Linux/Mac) and Android that verify:
  • Transaction arrives in Sentry with correct name and operation
  • Custom tags are present and removed tags are absent
  • Transaction data is present and removed data is absent
  • Child spans have correct operations, descriptions, and data
  • Span hierarchy (parent-child relationships) is correct
• Remove SentrySubsystem.spec.cpp, SentryTraceSampling.spec.cpp, and SentryTraceSamplingHandler.h unit tests replaced by e2e coverage
• Bump app-runner to include Get-SentrySpans and Get-SentryTestTransaction helpers that query the spans dataset
• Update package snapshot and integration test README
• Fix transaction/span tag removal on Android

Depends on:

• feat: Add utilities to query transaction data from Sentry app-runner#39

Related items:

• Replace unit tests that rely on subsystem re-initialization with e2e integration tests #1225

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🟢 Patch (bug fixes)

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