improvement(tree): Update table schema APIs to make underlying data representation safer / more opaque (microsoft#25979)

## Data format change

Adds an extra layer to the table tree. The previous structure:

```typescript
{
    columns: ListOfColumns;
    rows: ListOfRows;
}
```

The new structure:

```typescript
{
    table: {
        columns: ListOfColumns;
        rows: ListOfRows;
    }
}
```

This extra root field/node will make future migrations to a new
underlying format easier (we can migrate the node under the `table`
field, rather than requiring the end-user to migrate the entire table
node under its parent field in the application schema).

## API Safety Improvements

Some editing operations on the `columns` and `rows` lists would allow
users to make edits that would violate table invariants. The canonical
example of this is deleting an entry from the `columns` list without
removing corresponding cells from the `rows` list (cells live under
`Row` nodes).

Instead, the `Table` schema offers a series of safe editing APIs for the
table as a whole (e.g., `deleteColumn`, which includes the deletion of
corresponding cells).

But we still wish to surface a subset of list-like editing options for
the two lists. For example, since the ordering of these lists is
intended to be significant, we would like to support rearrangement of
elements within these lists. We would also like for users to be able to
subscribe to shallow change notifications on the lists to learn when
items have been inserted/removed/moved.

`columns` and `rows` have had their typing updated to be more
restrictive (forbidding direct insertion, deletion, and moving items
_between_ lists), while still affording the subset of list functionality
that is safe in terms of table invariants.

Author: Josmithr

examples/data-objects/table-tree/src/dataObject.ts

@@ -90,7 +90,7 @@ function getInitialTree(): Table {
 		},
 	});
 
-	return new Table({
+	return Table.create({
 		columns: [taskNameColumn, dateColumn, completedColumn],
 		rows: [row0, row1],
 	});

examples/utils/import-testing/src/test/importer.spec.ts

@@ -82,7 +82,7 @@ describe("import tests", () => {
 			row: Row,
 		}) {}
 
-		const _table = new Table({
+		const _table = Table.create({
 			columns: [
 				new Column({
 					props: {

packages/dds/tree/api-report/tree.alpha.api.md

@@ -28,6 +28,7 @@ export { asTreeViewAlpha } from "./tree.js";
 export { type SchemaStatics, schemaStatics } from "./schemaStatics.js";
 export {
 	SchemaFactory,
+	scoped,
 	type ScopedSchemaName,
 	type ObjectSchemaOptionsAlpha,
 	type ObjectSchemaOptions,

packages/dds/tree/src/simple-tree/api/index.ts

@@ -75,6 +75,7 @@ export {
 	type SchemaCompatibilityStatus,
 	type ITreeConfigurationOptions,
 	SchemaFactory,
+	scoped,
 	SchemaFactoryBeta,
 	type SchemaStaticsBeta,
 	SchemaFactoryAlpha,
@@ -248,6 +249,7 @@ export {
 	type ObjectFromSchemaRecord,
 	ObjectNodeSchema,
 	type ObjectNodeSchemaPrivate,
+	objectSchema,
 	isObjectNodeSchema,
 	type TreeObjectNode,
 	setField,