[clang] [CIR] Use SymbolTableCollection in LoweringPrepare's getCalledFunction (PR #195919)

[Henrich Lauko via cfe-commits]

xlauko wrote:

mlir::SymbolTableAnalysis stores this as attached ScopedSymbolTable to module I believe, which even survives between passes.

https://github.com/llvm/llvm-project/pull/195919