Use SymbolStringPtr for Symbol names in LinkGraph. This reduces string interning
on the boundary between JITLink and ORC, and allows pointer comparisons (rather
than string comparisons) between Symbol names. This should improve the
performance and readability of code that bridges between JITLink and ORC (e.g.
ObjectLinkingLayer and ObjectLinkingLayer::Plugins).

To enable use of SymbolStringPtr a std::shared_ptr<SymbolStringPool> is added to
LinkGraph and threaded through to its construction sites in LLVM and Bolt. All
LinkGraphs that are to have symbol names compared by pointer equality must point
to the same SymbolStringPool instance, which in ORC sessions should be the pool
attached to the ExecutionSession.
---------

Co-authored-by: Lang Hames <lhames@gmail.com>

ErrorAsOutParameter's Error* constructor supports cases where an Error might not
be passed in (because in the calling context it's known that this call won't
fail). Most clients always have an Error present however, and for them an Error&
overload is more convenient.

Identified with misc-include-cleaner.

Configure the plugin to automatically call the debugger rendezvous breakpoint `__jit_debug_register_code()` for every translation unit (enabled) or never at all (disabled). Default API and behavior remain unchanged.

If AutoRegisterCode is turned off, it's the client's own responsibility to call the rendezvous breakpoint function at an appropriate time.
Depending on the complexity of the debugger's rendezvous breakpoint implementation, this can provide significant performance improvements in cases where many debug objects are added in sequence.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D147310

Apparently, the refactor in 8b1771bd9f304be39d4dcbdcccedb6d3bcd18200 broke the logic behind formatv here:
```
  140736272011264 .rodata
  140736272015360 .text
  140736272011424 .eh_frame
```

Most ORC APIs work with ExecutorAddr by default since 8b1771bd9f3, so we don't
need to wrap these values in ExecutorAddr(...) calls any more.

Tested this with the new AArch32 backend on armv7l and it works without issues in GDB. The size of the load-address field is only 32-bit here, but we implicitly account for it by writing a ELFT::uint which is:
https://github.com/llvm/llvm-project/blob/release/16.x/llvm/include/llvm/Object/ELFTypes.h#L57

So, instead of adding a newly supported machine type, let's just drop this restriction althogether.

Sometimes it's useful to be able and debug code even without actual debug info, e.g. for setting breakpoints on function names.
This patch adds a new API option to make it possible in Orc.

The existing API and behavior remains unchanged: non-debug objects are not passed to exectuors.

DebugObjectManagerPlugin.cpp:372:8: error: unused variable 'ItInserted' [-Werror,-Wunused-variable]
  auto ItInserted = Sections.try_emplace(Name, std::move(Section));
       ^