ATLAS-5159: Export APIs: Exporting parent type doesn't export child type

[UmeshPatil-1]

ATLAS-5159

What changes were proposed in this pull request?

Background:
Exporting entities of a parent type (e.g., Referenceable) does not export entities of its child type (e.g., hive_table).
When attempting to export using the parent type with unique attributes, no child entities were returned, leading to incomplete exports.

Root Cause:

The export logic in StartEntityFetchByExportRequest did not properly handle abstract or parent types.
Methods like getEntitiesForMatchTypeType() and getEntitiesForMatchTypeUsingUniqueAttributes() only fetched concrete types when specified, ignoring child entities.

Changes Proposed:

1. Refactored StartEntityFetchByExportRequest to properly handle unique attribute lookups.
2. Updated getEntitiesForMatchTypeType() to include all subtypes of a parent type during export.
3. Simplified getEntitiesForMatchTypeUsingUniqueAttributes() for better performance and maintainability.
4. Updated getBindingsForTypeName() to ensure all subtypes are included in queries.
5. Improved logging and error handling for clarity.

Behavior Clarification: hive_table with Unique Attribute
When an export request specifies a concrete type such as hive_table along with a unique attribute (for example, qualifiedName):

• No subtype expansion occurs
• A single indexed lookup is executed using the unique attribute
• Only the matching entity GUID is returned

Impact:

• Exporting parent types like Referenceable now correctly includes all child entities.
• Maintains consistent behavior for all fetch types (FULL, INCREMENTAL, CONNECTED).
• Minimal impact on performance; no additional schema changes are required.

How was this patch tested?

• Maven Build:- Build Successfull.
• Manual testing of export requests with all three fetch types: FULL, INCREMENTAL, CONNECTED.
• Verified entity GUIDs are correctly returned for parent types and child entities,Concrete types with unique attributes (hive_table)
• Confirmed behavior for concrete types, abstract types, and invalid/misspelled types.
• Logs verified query execution, fetch type handling, and error reporting.

[chaitalicod]

Please update the doc with existing working scenario how it will work for eg for hive_table and same unique attribute https://1drv.ms/w/c/8e18c4b145719a2f/IQA5uOupz4B7Q5ibo_s6fwQ9AX_GGdv55cFs_35AImVvmfw?e=uzQfYV