uma: Improve memory modified after free panic messages

• Pass zone pointer to trash_ctor() and report zone name in the panic

message. It may be difficult to figyre out zone just by the item size.

• Do not pass user arguments to internal trash calls, pass thezone.
• Report malloc type name in the same unified panic message.
• Report corruption offset from the beginning of the items instead of

the full pointer. It makes panic message shorter and more readable.