fix: lose components types of components.d.ts

[ycs77]

fix #403
fix #419

1. The options.dts is unresolved, if the user not setting dts then will return undefined (not default value true), so must be use from the resolved option ctx.options.dts.
2. The ctx.generateDeclaration() can't resolve the UI components (get from resolvers) on first call on startup dev server, whether UI components in the components.d.ts exists or not, will be removed on startup dev server.

This PR changes to generate .d.ts file on startup server if ctx.options.dts is true and the file (like components.d.ts) exists.

(Of course, components.d.ts will still be updated normally when adding, updating files or trigger transform hook.)

---

No fix:

components.d.ts (before startup server):

declare module '@vue/runtime-core' {
  export interface GlobalComponents {
    ComponentA: typeof import('./src/components/ComponentA.vue')['default']
    VanRate: typeof import('vant/es')['Rate']
  }

}

Start dev/preview server if no setting options.dts:

declare module '@vue/runtime-core' {
  export interface GlobalComponents {
    ComponentA: typeof import('./src/components/ComponentA.vue')['default']
    VanRate: typeof import('vant/es')['Rate']
  }

}

Start dev/preview server if setting options.dts to true:

Warning

Missing VanRate (and other UI components) component type, the #403, #419 both is this status.

declare module '@vue/runtime-core' {
  export interface GlobalComponents {
    ComponentA: typeof import('./src/components/ComponentA.vue')['default']
  }

}

Apply PR (fixed):

components.d.ts (before startup server):

declare module '@vue/runtime-core' {
  export interface GlobalComponents {
    ComponentA: typeof import('./src/components/ComponentA.vue')['default']
    VanRate: typeof import('vant/es')['Rate']
  }

}

Start dev/preview server if no setting options.dts:

declare module '@vue/runtime-core' {
  export interface GlobalComponents {
    ComponentA: typeof import('./src/components/ComponentA.vue')['default']
    VanRate: typeof import('vant/es')['Rate']
  }

}

Start dev/preview server if setting options.dts to true:

declare module '@vue/runtime-core' {
  export interface GlobalComponents {
    ComponentA: typeof import('./src/components/ComponentA.vue')['default']
    VanRate: typeof import('vant/es')['Rate']
  }

}