sqflite_common_ffi 2.0.0-nullsafety.6

sqflite ffi based implementation, for desktop and units tests.

2.0.0-nullsafety.6

• nnbd support
• Improved sqlite shared lib loading mechanism to support alternate library.

1.1.1+2

• Fixes hot-restart lock issue
• Fixes missing databaseExists handler
• Don't load bundled sqlite3.dll on windows release mode.

1.1.0+1

• Use sqlite3 instead of moor_ffi

1.0.0+4

• Support extended result code exception

1.0.0+1

• Initial revision from sqflite_ffi_test experimentation