fix(insights): fix infinite spinner cache module landing (#71250)

The cache landing page table would contain an infinite spinner if no
data is available.
This is because the table requires two requests to populate, if the
first request has no data, the second requests would still be in the
`loading` state.

Also, if anybody remembers a more elegant way to do this, lmk! I feel
like this is came up a few times

static/app/views/performance/cache/cacheLandingPage.tsx

@@ -78,7 +78,7 @@ export function CacheLandingPage() {
   );
 
   const {
-    isLoading: isTransactionsListLoading,
+    isFetching: isTransactionsListFetching,
     data: transactionsList,
     meta: transactionsListMeta,
     error: transactionsListError,
@@ -107,12 +107,12 @@ export function CacheLandingPage() {
     data: transactionDurationData,
     error: transactionDurationError,
     meta: transactionDurationMeta,
-    isLoading: isTransactionDurationLoading,
+    isFetching: isTransactionDurationFetching,
   } = useMetrics(
     {
       search: `transaction:[${transactionsList.map(({transaction}) => `"${transaction}"`).join(',')}]`,
       fields: [`avg(transaction.duration)`, 'transaction'],
-      enabled: !isTransactionsListLoading && transactionsList.length > 0,
+      enabled: !isTransactionsListFetching && transactionsList.length > 0,
     },
     Referrer.LANDING_CACHE_TRANSACTION_DURATION
   );
@@ -194,7 +194,7 @@ export function CacheLandingPage() {
               <ModuleLayout.Full>
                 <TransactionsTable
                   data={transactionsListWithDuration}
-                  isLoading={isTransactionsListLoading || isTransactionDurationLoading}
+                  isLoading={isTransactionsListFetching || isTransactionDurationFetching}
                   sort={sort}
                   error={transactionsListError || transactionDurationError}
                   meta={meta}