Pending stuff for 9.0

[roji]

• Fix cloning logic on UnnestExpresion and co after Clean up and open table cloning logic dotnet/efcore#32665
• Unskip JsonQueryAdHocNpgsqlTest.Junk_in_json_basic_tracking (and the other) once Buffering error in JSON deserialization with junk data dotnet/efcore#32235 is fixed. Assuming that issue is backported, backport the unskip as well.
• Remove overrides in JsonTypesNpgsqlTest for unsigned numeric types (leaving this as this whole testing approach should go away with Comprehensive type testing for both serialization and querying dotnet/efcore#33521)
• Remove NpgsqlJsonElementHackConvention once Remove lookup of JsonTypeMapping via JsonElement dotnet/efcore#32192 is fixed.