[clang] [libclang/python] Add python bindings for PrintingPolicy (PR #120494)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

The PrintingPolicy constants just reflect the names from clang/include/clang/AST/PrettyPrinter.h.  For FullyQualifiedName specifically:

>  /// When true, print the fully qualified name of function declarations.
>  /// This is the opposite of SuppressScope and thus overrules it.

https://github.com/llvm/llvm-project/pull/120494