Follow-up from "feat: fab with highlight all/none"

The following discussion from !168 (merged) should be addressed:

@schneider210 started a discussion: (+1 comment)
I'd like to suggest to split our template: e.g. having a single component for the list, another one for the highlight buttons and an additional one for the (upcoming) anno-type toggles to keep the code leaner and maintainable this time. If you agree, I could turn it into a mixin along with the data needed herefore.

So this suggestion applies to the following lines as well dealing with the buttons.

Our complete template could finally look sth like this:
```
<template>
  <div
    v-if="annotations.length"
    class="q-ma-sm annotations"
  >
    <AnnotationTypes />

    <AnnotationList />

    <AnnotationOptions />
  </div>

  <div
    v-else
    class="q-pa-sm"
  >
    <Notification :message="$t(messages.none)" />
  </div>
</template>
```