ChangeFeed: Adds GA promotion for AllVersionsAndDeletes (Full Fidelity Change Feed) APIs

[ananth7592]

Summary

The Full Fidelity Change Feed (AllVersionsAndDeletes) feature has been in Preview since SDK version 3.18.0-preview (PR #2122). After multiple iterations of hardening, contract refinements, and CFP integration, the feature is ready for GA promotion.

This issue tracks removing the #if PREVIEW guards from 7 types/members to make them unconditionally public, along with updating the corresponding API contract files.

APIs to Promote

#	Type / Member	File	Line	Description
1	ChangeFeedMode.AllVersionsAndDeletes	src/ChangeFeed/ChangeFeedMode.cs	L56	Core entry point — the mode selector for FFCF
2	ChangeFeedItem<T>	src/Resource/FullFidelity/ChangeFeedItem.cs	L52	Wrapper for AVAD change items (current + previous + metadata)
3	ChangeFeedMetadata	src/Resource/FullFidelity/ChangeFeedMetadata.cs	L18	Metadata: operation type, LSN, conflict resolution timestamp, previous LSN
4	ChangeFeedOperationType	src/Resource/FullFidelity/ChangeFeedOperationType.cs	L12	Enum: Create, Replace, Delete
5	ChangeFeedPolicy	src/Resource/Settings/ChangeFeedPolicy.cs	L34	Retention policy configuration for the AVAD log
6	ChangeFeedPolicyDefinition	src/Fluent/Settings/ChangeFeedPolicyDefinition.cs	L12	Fluent builder for setting ChangeFeedPolicy on a container
7	ContainerProperties.ChangeFeedPolicy	src/Resource/Settings/ContainerProperties.cs	L382	Exposes ChangeFeedPolicy on ContainerProperties

Required Changes

For each file listed above:

1. Remove the #if PREVIEW / public / #else / internal / #endif block and replace with unconditional public.
2. Regenerate the GA API contract file (GenAPI) to include the newly public surface.
3. Verify that preview contract files are updated accordingly (remove the entries that moved to GA).

Notes

• Container.GetChangeFeedProcessorBuilderWithAllVersionsAndDeletes<T>() is already unconditionally public (no #if PREVIEW guard) — no changes needed there.
• The pull-model GetChangeFeedIterator<T>() accepting ChangeFeedMode is also already public, but passing AllVersionsAndDeletes is effectively blocked without Preview since the static property itself is internal without the flag.

Related PRs / Issues

• [Preview] Change Feed: Adds Full Fidelity support #2122 — Initial FFCF preview support
• [Preview] Change Feed: Adds SDK changes required for Full-Fidelity Change Feed #3197 — Core SDK changes for FFCF
• [Preview] Full Fidelity Change Feed: Adds new LatestVersion and AllVersionsAndDeletes to ChangeFeedMode #3596 — Renamed FullFidelity → AllVersionsAndDeletes
• ChangeFeedProcessor: Adds AllVersionsAndDeletes support to ChangeFeedProcessor #4370 — Added AVAD support to ChangeFeedProcessor
• ChangeFeedProcessor: Refactors AVAD metadata Contract #4380 — Renamed ChangeFeedItemChange → ChangeFeedItem
• CF/P AVAD: Fixes Deserialization of ChangeFeedItem and ChangeFeedMetadata to support System.Text.Json and Newtonsoft.Json #4618 — Fixed AVAD deserialization (STJ + Newtonsoft)
• Change feed: Adds id and pk to ChangeFeedMetadata for delete operations #5470 — Added id/pk to ChangeFeedMetadata for deletes