[DNM] feat(snapshots): Add Roborazzi support for Compose preview scanning

[runningcode]

Summary

Wires sentryUploadSnapshots<Variant> into the Roborazzi build flow when io.github.takahirom.roborazzi is applied, mirroring the existing Paparazzi integration. Roborazzi already provides @Preview-driven Robolectric test generation, so the plugin only configures it, pins its outputDir, and hooks recordRoborazzi<Variant> as a dependency of the upload task.

Behavior

When the user applies io.github.takahirom.roborazzi and sets sentry.snapshots.enabled = true:

• Auto-adds roborazzi-compose-preview-scanner-support and ComposablePreviewScanner:android to testImplementation.
• Configures Roborazzi's generateComposePreviewRobolectricTests from the shared snapshots.previews DSL (enable=true, packages from packageTrees, includePrivatePreviews pass-through) — using convention() so user values override.
• Pins roborazzi.outputDir to build/sentry/snapshots/<variant>/ (also via convention()).
• Hooks recordRoborazzi<Variant> as a dependency of sentryUploadSnapshots<Variant> and points its snapshotsPath at the staging dir.

If both app.cash.paparazzi and io.github.takahirom.roborazzi are applied to the same module, configuration fails with a clear message.

Notes

• No sidecar JSON is emitted on the Roborazzi path (per-image metadata is deferred to the ingestion side reading Roborazzi's native results-summary.json once upstream populates context_data with AndroidPreviewInfo). Paparazzi keeps its richer sidecar flow.
• Per-snapshot @SentrySnapshot.diffThreshold remains Paparazzi-only for now.

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- Add Roborazzi support for Compose preview scanning ([#1171](https://github.com/getsentry/sentry-android-gradle-plugin/pull/1171))

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