Some refactoring separated from #8825 for easier review.
# Important Notes
**ID types**
The new *synchronization IDs* will replace `ExprId` for `Ast` references in frontend logic. `ExprId` (now called `ExternalId`) is now used only for module serialization and engine communication. The graph database will maintain an index that is used to translate at the boundaries. For now, this translation is implemented as a type cast, as the IDs have the same values until the next PR.
- `AstId`: Identifies an `Ast` node.
- `NodeId`: A subtype of `AstId`.
- `ExternalId`: UUID used for serialization and engine communication.
**Other changes**:
- Immediate validation of `Owned` usage.
- Eliminate `Ast.RawCode`.
- Prepare to remove `IdMap` from yjsModel.
Further AST integration and API refinement before introducing the new synchronization mechanism.
closes#8609
# Important Notes
API changes:
- Renamed `Ast.parseExpression` / `Ast.parse` to better reflect their usage:
- `Ast.parse` returns a block or a single expression, depending on its input; this is convenient for expressions expected to be single-line.
- `Ast.parseBlock` always treats its input as a block; this is suitable for parsing a file.
- `astExtended` is no longer needed to access span information. `Ast.span` provides access to the value when appropriate (the project's committed modules have spans; uncommitted changes or other parsed expressions don't).
- `SourceRange` is now used everywhere in place of `ContentRange`--the two types had the same definition.
Features:
- Fix CodeEditor viewing.
Implementation improvements:
- Updated widget update handlers (#8545) implementation to Ast API.
- Integrated `imports` more thoroughly with new AST APIs.
- More tests.
