We defend against a direct cycle where a base class ValueObject is its
own parent, but not against a longer base cycle. This cycle requires
that some value's Type includes a base class, and that base class is in
a class hierarchy that cycles back to the original base class.

I wrote a test case that creates a cycle in the class hierarchy by
dynamically overwriting the superclass of an object, but I can't
reproduce the crash. I can't think of any other way to make a real
object that behaves that way. Maybe is a type system problem in making
up the type for whatever type we're trying to ingest here.

While unsatisfying, without a reproducer this is the best we can do for
now.

rdar://140293233

Fix the rare case where an ObjC class has ivars but no methods. The fix is to not early
return when a class has no method list.

The only difference from the original PR are the added BRIEF and
FULL_DOCS arguments to define_property, which are required for
cmake<3.23.

Causes failures on several bots.

This reverts commits 714b2fdf3a385e5b9a95c435f56b1696ec3ec9e8 and
e7c1da7c8ef31c258619c1668062985e7ae83b70.

Some inter-plugin dependencies are okay, others are not. Yet others not,
but we're sort of stuck with them. The idea is to be able to prevent
backsliding while making sure that acceptable dependencies are..
accepted. For context, see
https://github.com/llvm/llvm-project/pull/139170 and the attached
changes to the documentation.

If we're not touching them, we don't need to do anything special to pass
them along -- with one important caveat: due to how cmake arguments
work, the implicitly passed arguments need to be specified before
arguments that we handle.

This isn't particularly nice, but the alternative is enumerating all
arguments that can be used by llvm_add_library and the macros it calls
(it also relies on implicit passing of some arguments to
llvm_process_sources).

The problem was in calling GetLoadAddress on a value in the error state,
where `ValueObject::GetLoadAddress` could end up accessing the
uninitialized "address type" by-ref return value from `GetAddressOf`.
This probably happened because each function expected the other to
initialize it.

We can guarantee initialization by turning this into a proper return
value.

I've added a test, but it only (reliably) crashes if lldb is built with
ubsan.

We're reading from the object's vtable to determine the pointer to the
full object. The vtable is normally in the "rodata" section of the
executable, which is often not included in the core file because it's
not supposed to change and the debugger can extrapolate its contents
from the executable file. We weren't doing that.

This patch changes the read operation to use the target class (which
falls back onto the executable module as expected) and adds the missing
ReadSignedIntegerFromMemory API. The fix is tested by creating a core
(minidump) file which deliberately omits the vtable pointer.

Fixes parsing of an ObjC type encoding such as `{?="a""b"}`. Parsing of such a type
encoding would lead to an assert. This was observed when running `language objc
class-table dump`.

The function `ReadQuotedString` consumes the closing quote, however one of its two
callers (`ReadStructElement`) was also consuming a quote. For the above type encoding,
where two quoted strings occur back to back, the parser would unintentionally consume
the opening quote of the second quoted string - leaving the remaining text with an
unbalanced quote.

This changes fixes `ReadStructElement` to not consume a quote after calling
`ReadQuotedString`.

For callers to know whether a string was successfully parsed, `ReadQuotedString` now
returns an optional string.