Change index key format to no longer use BSON in WiredTiger.
- much faster key comparison
- reduced storage size for indexes
- take much better advantage of WT key prefix compression
- no longer require custom collator, which means stock WT tools like repair work with no modification
As this is an on-disk format change, indexes created before this change with WT will no longer be usable without running:
mongod --storageEngine wiredTiger --repair