fix: types aren't working when @vue/runtime-core is not installed

fixes vuejs/language-tools#3107
fixes #355

Author: wenfangdu

src/core/declaration.ts

@@ -118,11 +118,9 @@ export function getDeclaration(ctx: Context, filepath: string, originalImports?:
     ? `export {}
 
 declare module 'vue' {`
-    : `import '@vue/runtime-core'
+    : `export {}
 
-export {}
-
-declare module '@vue/runtime-core' {`
+declare module 'vue' {`
 
   let code = `/* eslint-disable */
 /* prettier-ignore */

test/__snapshots__/dts.test.ts.snap

@@ -6,11 +6,9 @@ exports[`dts > components only 1`] = `
 // @ts-nocheck
 // Generated by unplugin-vue-components
 // Read more: https://github.com/vuejs/core/pull/3399
-import '@vue/runtime-core'
-
 export {}
 
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface GlobalComponents {
     RouterLink: typeof import('vue-router')['RouterLink']
     RouterView: typeof import('vue-router')['RouterView']
@@ -26,11 +24,9 @@ exports[`dts > directive only 1`] = `
 // @ts-nocheck
 // Generated by unplugin-vue-components
 // Read more: https://github.com/vuejs/core/pull/3399
-import '@vue/runtime-core'
-
 export {}
 
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface ComponentCustomProperties {
     vLoading: typeof import('test/directive/Loading')['default']
   }
@@ -44,11 +40,9 @@ exports[`dts > getDeclaration 1`] = `
 // @ts-nocheck
 // Generated by unplugin-vue-components
 // Read more: https://github.com/vuejs/core/pull/3399
-import '@vue/runtime-core'
-
 export {}
 
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface GlobalComponents {
     RouterLink: typeof import('vue-router')['RouterLink']
     RouterView: typeof import('vue-router')['RouterView']
@@ -122,11 +116,9 @@ exports[`dts > writeDeclaration - keep unused 1`] = `
 // @ts-nocheck
 // Generated by unplugin-vue-components
 // Read more: https://github.com/vuejs/core/pull/3399
-import '@vue/runtime-core'
-
 export {}
 
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface GlobalComponents {
     RouterLink: typeof import('vue-router')['RouterLink']
     RouterView: typeof import('vue-router')['RouterView']
@@ -148,11 +140,9 @@ exports[`dts > writeDeclaration 1`] = `
 // @ts-nocheck
 // Generated by unplugin-vue-components
 // Read more: https://github.com/vuejs/core/pull/3399
-import '@vue/runtime-core'
-
 export {}
 
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface GlobalComponents {
     RouterLink: typeof import('vue-router')['RouterLink']
     RouterView: typeof import('vue-router')['RouterView']

test/dts.test.ts

@@ -52,7 +52,7 @@ const _directive_loading = _resolveDirective("loading")`
     await writeFile(
       filepath,
       `
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface GlobalComponents {
     SomeComp: typeof import('test/component/SomeComp')['default']
     TestComp: typeof import('test/component/OldComp')['default']
@@ -128,11 +128,9 @@ const _directive_loading = _resolveDirective("loading")`
 // generated by unplugin-vue-components
 // We suggest you to commit this file into source control
 // Read more: https://github.com/vuejs/core/pull/3399
-import '@vue/runtime-core'
-
 export {}
 
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface GlobalComponents {
     ComponentA: typeof import('./src/components/ComponentA.vue')['default']
     ComponentB: typeof import('./src/components/ComponentB.vue')['default']
@@ -151,11 +149,9 @@ declare module '@vue/runtime-core' {
 // generated by unplugin-vue-components
 // We suggest you to commit this file into source control
 // Read more: https://github.com/vuejs/core/pull/3399
-import '@vue/runtime-core'
-
 export {}
 
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface GlobalComponents {
     ComponentA: typeof import('./src/components/ComponentA.vue')['default']
     'IMdi:diceD12': typeof import('~icons/mdi/dice-d12')['default']
@@ -174,11 +170,9 @@ declare module '@vue/runtime-core' {
 // generated by unplugin-vue-components
 // We suggest you to commit this file into source control
 // Read more: https://github.com/vuejs/core/pull/3399
-import '@vue/runtime-core'
-
 export {}
 
-declare module '@vue/runtime-core' {
+declare module 'vue' {
   export interface GlobalComponents {
     ComponentA: typeof import('./src/components/ComponentA.vue')['default']
     'IMdi:diceD12': typeof import('~icons/mdi/dice-d12')['default']