This patch uses *Set::insert_range and a range constructor of DenseSet
to clean up the code to populate sets.

This rename follows the proposed wording in P3310R5, which introduces
the term 'strict pack match' to refer to the same thing.

Class templates might be only instantiated when they are required to be
complete, but checking the template args against the primary template is
immediate.

This result is cached so that later when the class is instantiated,
checking against the primary template is not repeated.

The 'MatchedPackOnParmToNonPackOnArg' flag is also produced upon
checking against the primary template, so it needs to be cached in the
specialziation as well.

This fixes a bug which has not been in any release, so there are no
release notes.

Fixes #125290

Since https://reviews.llvm.org/D141827 this field gets used
to print type names. Thus propagate it after importing TemplateArguments
from modules.

**Testing**

* Confirmed that this fixes the ongoing `import-std-module` test
  failures.

Differential Revision: https://reviews.llvm.org/D142714

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

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated.  The intent is to reduce
the amount of manual work required in migrating from Optional to
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

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.

The pointer is dereferenced immediately, so assert the cast is correct instead of returning nullptr