specify _all as target in ClearCacheModal

When none of the indices are selected, ClearCacheModal makes call to
`//_cache/clear` path. Here, the intention is to clear the cache for
all indices, let's make it explicit by passing `_all` as target.

New call: `/_all/_cache/clear`

Signed-off-by: Rohit Ashiwal <[email protected]>

public/containers/ClearCacheModal/ClearCacheModal.tsx

@@ -113,7 +113,7 @@ export default function ClearCacheModal(props: ClearCacheModalProps) {
         const result = await services.commonService.apiCaller({
           endpoint: "indices.clearCache",
           data: {
-            index: unBlockedItems.join(","),
+            index: unBlockedItems.join(",") || "_all",
           },
         });
         if (result && result.ok) {