MDEV-15091 : Windows, 64bit: reenable and fix warning C4267 (conversion from 'size_t' to 'type', possible loss of data)

Handle string length as size_t, consistently (almost always:))
Change function prototypes to accept size_t, where in the past
ulong or uint were used. change local/member variables to size_t
when appropriate.

This fix excludes rocksdb, spider,spider, sphinx and connect for now.