Upgrade dependency to LLVM 17

[varungandhi-src]

At the time of writing, we're missing several months worth of changes from upstream.

[JohnnyMorganz]

Hi, has there been any progress with this?
We are trying to index a Bazel codebase with c++23 enabled and seeing compiler diagnostic errors:

error: invalid value 'c++23' in '-std=c++23'
note: use 'c++98' or 'c++03' for 'ISO C++ 1998 with amendments' standard
note: use 'gnu++98' or 'gnu++03' for 'ISO C++ 1998 with amendments and GNU extensions' standard
note: use 'c++11' for 'ISO C++ 2011 with amendments' standard
note: use 'gnu++11' for 'ISO C++ 2011 with amendments and GNU extensions' standard
note: use 'c++14' for 'ISO C++ 2014 with amendments' standard
note: use 'gnu++14' for 'ISO C++ 2014 with amendments and GNU extensions' standard
note: use 'c++17' for 'ISO C++ 2017 with amendments' standard
note: use 'gnu++17' for 'ISO C++ 2017 with amendments and GNU extensions' standard
note: use 'c++20' for 'ISO C++ 2020 DIS' standard
note: use 'gnu++20' for 'ISO C++ 2020 DIS with GNU extensions' standard
note: use 'c++2b' for 'Working draft for ISO C++ 2023 DIS' standard
note: use 'gnu++2b' for 'Working draft for ISO C++ 2023 DIS with GNU extensions' standard

... later compiler errors about c++23 features e.g. `no member named 'to_underlying' in namespace 'std'` 

Is it related to this issue of an old llvm version? Our toolchain is configured with an llvm 17 compiler, but maybe the version used in scip-clang is important.