This change first attempts to resolve a schematic referenced via the external schematic rule from the requesting schematic collection. This allows schematic packages that are direct dependencies of another schematic package to be used with the external schematic rule without manual package resolution code within the schematic.
Closes#18098Closes#11026
BREAKING CHANGE:
Removed several deprecated APIs:
- EngineHost `listSchematics` has been removed in favour of `listSchematicNames`.
- `FileSystemSink` - Use the new virtualFs.Host classes from `@angular-devkit/core`.
- `optimize` function has been remove as trees are automaticlly optimized.
- `DryRunSink` deprecated constructor that allowed to provide a directory path has been removed. Provide a `virtualFs.Host` instead.
