[Autocomplete][Feature]add props support

[baiyaaaaa]

Please make sure these boxes are checked before submitting your PR, thank you!

• Make sure you follow Element's contributing guide (中文 | English).
• Make sure you are merging your commits to dev branch.
• Add some descriptions and refer relative issues for you PR.

#5136

[davidweining2333]

指南中的这种用法并不生效，会导致报错
附我的代码片段

<el-autocomplete class="inline-input search-box" v-model="filterModel.search.value" :fetch-suggestions="querySearch" :placeholder="filterModel.search.holder" :on-icon-click="handleIconClick" @select="handleSelect" icon="search">
                        <template slot-scope="props">
                            <div class="name">{{ props.item.value }}</div>
                            <span class="addr">{{ props.item.key }}</span>
                        </template>
                    </el-autocomplete>