[clang] [clang][test] Move offload tools tests to clang/test/OffloadTools (PR #198434)

[Yury Plyakhin via cfe-commits]

YuriPlyakhin wrote:

> > The spirv-tools feature/substitution setup is carried over from Tooling's lit.local.cfg into a new lit.local.cfg in clang-linker-wrapper/, since the parent clang/test/lit.cfg.py does not set up that feature. The dead spirv-tools block is removed from Tooling/lit.local.cfg now that no tests there depend on it.
> 
> Why do OffloadTools tests depend on spirv-tools? I expect only SPIR-V backend tests need those.

@bader , 
```
# executed command: clang-linker-wrapper --host-triple=x86_64-unknown-linux-gnu --linker-path=/usr/bin/ld openmp-spirv.cpp.tmp.host.o -o clang-linker-wrapper/Output/openmp-spirv.cpp.tmp

# .---command stderr------------
# | clang: error: cannot find SPIR-V Tools binary 'spirv-link', which is required for SPIR-V compilation. It can be obtained from your system package manager or from KhronosGroup/SPIRV-Tools on GitHub
# | /localdisk2/yplyakhi/llvm-project/build/bin/clang-linker-wrapper: error: 'clang' failed
# `-----------------------------
# error: command failed with exit status: 1
```
this is my understanding:
`clang-linker-wrapper` runs `clang --target=spirv64-intel`, and the driver selects SPIRV::Linker for the link step, which resolves to `spirv-link`.

https://github.com/llvm/llvm-project/pull/198434