fix abi struct layout bugs and bind missing db.h functions

[guycipher]

the native config dbstats and stats structs were missing trailing fields causing out of bounds reads and writes and stack corruption when opening a database and reading database stats. added the finish compactions on close field to config the eight write amplification counters to dbstats and the seven write amplification counters to stats and exposed them all on the managed types

fixed register comparator which always failed because it passed a null function pointer. you can now register a custom managed comparator delegate or alias one of the six built in comparators under a new name

bound the remaining db.h surface that was missing init and finalize raise open file limit compression available cancel background work cf config load and save to ini and the s3 create config factory with tls and multipart options. added the busy error code

added sixteen tests covering the new surface fixed a stale max concurrent flushes assertion extended the csharp reference docs and bumped the package version to zero six two