This patch replace all in-memory objects of DebugValueAddrInst with
DebugValueInst + op_deref, and duplicates logics that handles
DebugValueAddrInst with the latter. All related check in the tests
have been updated as well.
Note that this patch neither remove the DebugValueAddrInst class nor
remove `debug_value_addr` syntax in the test inputs.
There are certain conditions that cause them to reference
non-public properties, in particular if the property
wrapper is implemented via a subscript taking a keypath.
Instead of trying to detect this specific case though (and
possibly missing others), I'm just going to decree that
'modify' is never going to be transparent for property
wrappers.
Fixes <rdar://problem/57609867>.
