Schema Import Failure: RemapManager fails during cleanup

[RohitPtnkr1996]

A user reported their major schema upgrade was failing with the error "Failed to find class SILO for ensuring persisted property maps."

On further investigation, this was due to a very specific schema evolution scenario:

1. Base schema contains a class hierarchy.
2. Minor upgrade where the leaf class overrides the property and adds a child class which inherits the overridden property.
3. Major upgrade where the overridden property is removed from the parent and the child class is also deleted.

When deleting the property override, the remap manager collects the remap info for the child class using its property map.
Later, the child class gets deleted.
On cleanup and remapping, when the remap manager tries to restore the saved property map info, it fails to find the child class and throws the error.

Fixes https://github.com/iTwin/itwinjs-backlog/issues/1857

[Copilot]

Pull request overview

Fixes a schema remapping cleanup failure when a class is deleted after remap info for its property maps has been collected (specific schema evolution scenario involving property overrides + derived class deletion).

Changes:

• Add regression test covering “delete property override + delete derived class” for both regular and V8 legacy schema import paths.
• Prevent remap cleanup from attempting to restore property maps for classes that get deleted during the same import.
• Add a VS Code debug launch configuration for iModelConsole.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.

File	Description
iModelCore/iModelPlatform/Tests/DgnProject/NonPublished/SchemaRemap_Test.cpp	Adds a regression test to reproduce and validate the remap cleanup fix.
iModelCore/ECDb/ECDb/SchemaWriter.cpp	Calls into RemapManager during class deletion to avoid restoring mappings for deleted classes.
iModelCore/ECDb/ECDb/RemapManager.h	Adds a helper to drop cleaned mapping info for a class being deleted.
.vscode/launch.json	Adds a new debug configuration for iModelConsole.