Add Download results in each accordion results in search multiple + add tests

src/app/search-multiple/components/index.ts

...multiple/components/result/datasets-result.component.html

...h-multiple/components/result/datasets-result.component.ts

...multiple/components/result/download-section.component.css

...ultiple/components/result/download-section.component.html

...iple/components/result/download-section.component.spec.ts

...-multiple/components/result/download-section.component.ts

...search-multiple/containers/result-multiple.component.html

src/app/search/components/index.ts

src/app/search/components/result/download.component.html

src/app/search/components/result/download.component.spec.ts

src/app/search/components/result/download.component.ts