Incorporate signia as @tldraw/state (#1620)

It tried to get out but we're dragging it back in. 

This PR brings [signia](https://github.com/tldraw/signia) back into
tldraw as @tldraw/state.

### Change Type

- [x] major

---------

Co-authored-by: David Sheldrick <d.j.sheldrick@gmail.com>

packages/editor/src/lib/components/ShapeIndicator.tsx

@@ -1,11 +1,7 @@
+import { useStateTracking, useValue } from '@tldraw/state'
 import { TLShape, TLShapeId } from '@tldraw/tlschema'
 import classNames from 'classnames'
 import * as React from 'react'
-import {
-	// @ts-expect-error 'private' export
-	useStateTracking,
-	useValue,
-} from 'signia-react'
 import { useEditor } from '../..'
 import type { Editor } from '../editor/Editor'
 import { ShapeUtil } from '../editor/shapes/ShapeUtil'