dbg: introduce lj-ctype command, extend cdata dump

This patch extends dumped information for the given cdata object. Now
it resolves the given `CType` and prints it in the format similar to the
`__tostring` metamethod. The `lj-ctype` command is introduced to dump
this information where there is only the `CType` pointer but no cdata
associated with it.

`__or__` and `__ror__` metamethods are monkey-patched for the LLDB value
object. In `__sub__` metamethod for LLDB pointers `GetPointeeType()` is
used to get the pointee type instead of the incorrectly used
`GetDereferencedType()` which always returns the same type with size 8.
Casting from negative values to the unsigned values is supported to
check `CTF_UCHAR`.

Part of tarantool/tarantool#4808

Author: Buristan