m_disassembly_range was used only to prune the list of breakpoints to
those that are in the current function. This isn't really necessary, as
the list is only used to highlight instructions with breakpoints on
them, and an unpruned list works just as well for that.

The shouldn't make things slower, since we still needed through iterate
through all breakpoints to create the list, and I doubt anyone will
notice the memory used to store the extra breakpoints.

This patch improves the synchronization of the debugger's output and error
streams using two new abstractions: `LockableStreamFile` and
`LockedStreamFile`.

 - `LockableStreamFile` is a wrapper around a `StreamFile` and a mutex. Client
   cannot use the `StreamFile` without calling `Lock`, which returns a
   `LockedStreamFile`.

 - `LockedStreamFile` is an RAII object that locks the stream for the duration
   of its existence.  As long as you hold on to the returned object you are
   permitted to write to the stream. The destruction of the object
   automatically flush the output stream.

 - Remove _ap (auto_ptr) suffix with _up (unique_ptr) suffix
 - Move forward declaration from IOHandler.h to IOHandlerCursesGUI.h
 - Move curses namespace under lldb_private

Motivated by Alex' comment in #126630.

ValueObject is part of lldbCore for historical reasons, but conceptually
it deserves to be its own library. This does introduce a (link-time) circular
dependency between lldbCore and lldbValueObject, which is unfortunate
but probably unavoidable because so many things in LLDB rely on
ValueObject. We already have cycles and these libraries are never built
as dylibs so while this doesn't improve the situation, it also doesn't
make things worse.

The header includes were updated with the following command:

```
find . -type f -exec sed -i.bak "s%include \"lldb/Core/ValueObject%include \"lldb/ValueObject/ValueObject%" '{}' \;
```

To support detecting MD5 checksum mismatches, deal with SupportFiles
rather than a plain FileSpecs in the SourceManager.

To support detecting MD5 checksum mismatches, store a SupportFile rather
than a plain FileSpec in SourceManager::File.

This is another step towards supporting DWARF5 checksums and inline
source code in LLDB. This is a reland of #85468 but without the
functional change of storing the support file from the line table (yet).

Reverts llvm/llvm-project#85468 because @slackito reports this broke
stepping in one of their tests [1] and this patch was meant to be NFC.

[1]
https://github.com/llvm/llvm-project/commit/d5a277d309e92b1d3e493da6036cffdf815105b1#commitcomment-139991120

This is another step towards supporting DWARF5 checksums and inline
source code in LLDB.

Change GetNumChildren()/CalculateNumChildren() methods return
llvm::Expected

This is an NFC change that does not yet add any error handling or change
any code to return any errors.

This is the second big change in the patch series started with
https://github.com/llvm/llvm-project/pull/83501

A follow-up PR will wire up error handling.