fix(compiler-sfc): defineProps() should work with multiple declarations

[HcySunYang]

Fix: #3739

[Sociosarbis]

I found another bug on current VariableDeclaration string removal implementation.

If user has defineEmit after defineProps or vice versa and the number of declarations is 2 like the following code.

const props = defineProps({
  foo: String
}),
 myEmit = defineEmit(['bar'])

The above code would be compiled to

const props = __props
const 

return { props, myEmit }

which isn't valid too.

[HcySunYang]

I found another bug on current VariableDeclaration string removal implementation.

@Sociosarbis Now this PR can fix that.

[yyx990803]

See a slightly more efficient fix in 62c1b2f (avoids filter and indexOf calls)