Updated debugging metadata for ty_nil and ty_bot

ty_nil will now report as "()" in gdb
ty_bot will now report as "!" in gdb

Added test to confirm basic types debugging metadata.

This fixes #9226
auto merge of #10235 : mletterle/rust/issue-9226, r=jdm

ty_nil will now report as "()" in gdb
ty_bot will now report as "!" in gdb

Added test to confirm basic types debugging metadata.

This fixes #9226