sdk-version-19.0.0

Document ProductImprovement control in v19.0.0

Summary:
Document Android's AutoLogProductImprovementEnabled control in the 19.0.0 release notes, matching iOS D124863980 and the requested release-note placement.

The new Added entry describes diagnostic product improvement data, default true, the exact Android manifest key, the public runtime setter/getter, persistence across launches and precedence over the manifest, and independence from metadata collection and automatic app-event logging. It explicitly states that this patch introduces the control only: the SDK does not yet collect or send product improvement data.

Preserve the existing 19.0.0 metadata and automatic-event notes, empty Unreleased section, historical release notes, and comparison links. No version bump or runtime changes are included in this documentation commit.

Reviewed By: Zhiyi-Zhang

Differential Revision: D124874130

fbshipit-source-id: b695e3554919cce56dea509125c03eb41d2de60d