This patch replaces (llvm::|)Optional< with std::optional<.  I'll post
a separate patch to clean up the "using" declarations, #include
"llvm/ADT/Optional.h", etc.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

This patch adds #include <optional> to those files containing
llvm::Optional<...> or Optional<...>.

I'll post a separate patch to actually replace llvm::Optional with
std::optional.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

When a process gets restarted TypeSystem objects associated with it
may get deleted, and any CompilerType objects holding on to a
reference to that type system are a use-after-free in waiting. Because
of the SBAPI, we don't have tight control over where CompilerTypes go
and when they are used. This is particularly a problem in the Swift
plugin, where the scratch TypeSystem can be restarted while the
process is still running. The Swift plugin has a lock to prevent
abuse, but where there's a lock there can be bugs.

This patch changes CompilerType to store a std::weak_ptr<TypeSystem>.
Most of the std::weak_ptr<TypeSystem>* uglyness is hidden by
introducing a wrapper class CompilerType::WrappedTypeSystem that has a
dyn_cast_or_null() method. The only sites that need to know about the
weak pointer implementation detail are the ones that deal with
creating TypeSystems.

rdar://101505232

Differential Revision: https://reviews.llvm.org/D136650

Familiar story, callers are either checking upfront that the pointer
wasn't null or not checking at all. SetValueFromData itself didn't
check either.

So make the parameter a ref and fixup the few places where a nullptr
check seems needed.

Depends on D135668

Reviewed By: clayborg

Differential Revision: https://reviews.llvm.org/D135670

This was inadvertedly changed (bad search&replace) when I was removing
the LLDBLOG macros.

SetValueFromCString and SetData methods return false if register can't
be written but they don't set a error message. It sometimes confuses
callers of these methods because they try to get the error message in case of
failure but Status::AsCString returns nullptr.

For example, lldb-vscode crashes due to this bug if some register can't
be written. It invokes SBError::GetCString in case of error and doesn't
check whether the result is nullptr (see request_setVariable implementation in
lldb-vscode.cpp for more info).

Reviewed By: labath, clayborg

Differential Revision: https://reviews.llvm.org/D120319

Most of our code was including Log.h even though that is not where the
"lldb" log channel is defined (Log.h defines the generic logging
infrastructure). This worked because Log.h included Logging.h, even
though it should.

After the recent refactor, it became impossible the two files include
each other in this direction (the opposite inclusion is needed), so this
patch removes the workaround that was put in place and cleans up all
files to include the right thing. It also renames the file to LLDBLog to
better reflect its purpose.

Update GetRegisterInfoByName() methods to support getting registers
by a generic name independently of alt_name entries in the register
context.  This makes it possible to use generic names when interacting
with gdbserver (that does not supply alt_names).  It also makes it
possible to remove some of the duplicated information from register
context declarations and/or use alt_names for another purpose.

Differential Revision: https://reviews.llvm.org/D108554

Replace default bodies of special member functions with = default;

$ run-clang-tidy.py -header-filter='lldb' -checks='-*,modernize-use-equals-default' -fix ,

https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-equals-default.html

Differential revision: https://reviews.llvm.org/D104041