refactor(compiler): further extract babel ast utilities

packages/compiler-sfc/src/index.ts

@@ -4,11 +4,10 @@ export { compileTemplate } from './compileTemplate'
 export { compileStyle, compileStyleAsync } from './compileStyle'
 export { compileScript } from './compileScript'
 export { rewriteDefault } from './rewriteDefault'
-export { generateCodeFrame } from '@vue/compiler-core'
+export { generateCodeFrame, walkIdentifiers } from '@vue/compiler-core'
 
 // Utilities
 export { parse as babelParse } from '@babel/parser'
-export { walkIdentifiers } from './compileScript'
 import MagicString from 'magic-string'
 export { MagicString }
 export { walk } from 'estree-walker'