Revert "Code Cleanup: RideFileCache remove mallocs"

This reverts commit 6fdc55528f6f5bf704b93a7f101634c3f4908928.

The performance decrease is considerable. Using mallocs across
my personal ride collection takes 5:19 to compute all the caches.
Using the QVector equivalent took 22:40.

Need to consider looking at QVector across the GC codebase.