docs: remove unimplemented ItemBatcher documentation from map.md

[abhu85]

Summary

Fixes #304

The ItemBatcher feature is not yet implemented and is reserved for future use. As confirmed by the SDK developer in the issue, this documentation should not have been included. This PR removes all references to batching functionality from the map operations documentation to prevent users from trying to use an unimplemented feature.

Changes

• Remove "Item batching" terminology definition
• Remove "Batching support" from Key features list
• Remove "Batching items" section from Advanced patterns
• Remove ItemBatcher import and usage from Configuration example
• Remove item_batcher parameter documentation from MapConfig parameters
• Remove batching-related FAQ entry ("How does batching work?")
• Update Best practices to remove "Batch for efficiency" tip
• Update Performance tips to remove batching-related code example and references
• Update method signature to remove BatchedInput type hint from func parameter
• Update various text references from "batching or processing in chunks" to just "processing in chunks"

Test Plan

• Documentation changes only - no code changes
• All remaining code examples are valid (they don't use removed features)
• Documentation structure and links remain intact
• Verified all batching references have been removed

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