Allow sharing of S3 file cache between cluster nodes or between restarts

The S3BinaryManager (and other binary managers based on CachingBinaryManager) use a filesystem cache of already-downloaded files to avoid doing it every time (nxbincache). This cache currently isn't sharable between cluster nodes.

Since NXP-18369 the cache is now still functional if shared across cluster nodes, however because it has a random name decided at startup it can't really be shared or even reused between restarts.

-> Make the cache use a fixed name to allow sharing or reuse.