Add SCCHighlightPass to propagate and display IsHighlighted functions

[rmrayakar]

This patch introduces a new SCC-level LLVM pass named SCCHighlightPass and a custom function attribute IsHighlighted.

• The pass traverses the call graph using scc_iterator.
• If any function in a strongly connected component (SCC) has the IsHighlighted attribute, the pass propagates this attribute to all other functions in the same SCC.
• It then displays all functions with the IsHighlighted attribute in a well-formatted table that includes:
  • Demangled function name and full signature
  • Source filename and line number (from debug metadata)
  • Function size (LOC)

This pass aids in debugging and understanding call graph propagation from selectively marked functions.

Fixes #28

Commands Used to Run:

Step 1: Build the LLVM Plugin
Make sure you're in the root of the llvm-project directory and run:
cd build
ninja

Step 2: Run the custom LLVM pass from llvm-project directory
./build/bin/opt -load-pass-plugin ./build/lib/SCCHighlightPass.so -passes=highlight-scc -disable-output < llvm/test/Transforms/SCCHighlight/test.ll