feat: re-enable Telemetry Processor and simplify setup

[giortzisg]

Description

This PR re-enables support for the Telemetry Processor and includes simplifying it's setup.

• Switch client-side DSN storage and parsing from the public sentry.Dsn wrapper to internal/protocol.Dsn during client initialization.
• Update envelope headers and transport code to carry *protocol.Dsn directly instead of converting back and forth to strings.
• Move the telemetry processor setup decision into NewClient, so client startup chooses one path up front:
  • use the telemetry processor when telemetry buffering is enabled and no custom transport is provided
  • otherwise fall back to the legacy transport plus the existing batch log/metric processors
• Remove now-redundant guard logic from setupTelemetryProcessor, since the caller is now responsible for deciding whether that path is valid.
• Update tests to reflect the new empty-DSN behavior, where the telemetry processor is still initialized and backed by the internal noop transport.
• Make the client reports integration test wait for asynchronously delivered reports instead of assuming they are immediately present.

Issues

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Changelog Entry

• Re-enable Telemetry Processor by default. To disable the behavior use the DisableTelemetryBuffer flag.
• Simplify client DSN storage to internal/protocol.Dsn and make it safe to access.

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

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New Features ✨

• Re-enable Telemetry Processor by default. To disable the behavior use the DisableTelemetryBuffer flag. by giortzisg in #1254
• Simplify client DSN storage to internal/protocol.Dsn and make it safe to access. by giortzisg in #1254

Internal Changes 🔧

Deps

• Bump go.opentelemetry.io/otel/sdk from 1.40.0 to 1.43.0 in /otel by dependabot in #1256
• Bump go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp from 1.40.0 to 1.43.0 in /otel/otlp by dependabot in #1255

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[Litarnus]

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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^{Reviewed by Cursor Bugbot for commit 3d172e2. Configure here.}

[cursor]

Moved setupIntegrations before Transport initialization breaks custom integrations

Medium Severity

setupIntegrations() was moved from after transport setup to before it. Custom integrations provided via options.Integrations that access client.Transport in their SetupOnce callback will now get a nil Transport, which was previously always set. This is a behavioral regression since client.Transport is a public field that integrations could reasonably access during setup.

 

^{Reviewed by Cursor Bugbot for commit 3d172e2. Configure here.}