[clang] [OpenMP] Parse and Sema support for declare target in local scope (PR #83223)

[Sandeep Kosuri via cfe-commits]

sandeepkosuri wrote:

> One big question - why do we need it in function scope for clang?

According to the spec, it is not explicitly mentioned that the `declare target` placement is not allowed inside a function scope. And I came across this [sollve test case](https://github.com/SOLLVE/sollve_vv/blob/master/tests/5.0/declare_target/test_declare_target_nested_functions.c) which made me realise that this should be allowed.

https://github.com/llvm/llvm-project/pull/83223