Fix iterator invalidation crashes

[halalboro]

Summary

• Fix std::length_error: basic_string::_M_create crash in ep2c-opt when compiling nfchain.c with --target rtl
• The crash occurred during the --ep2-pipeline-canon -ep2-handler-repl -ep2-global-to-partition pass pipeline

Root Cause
Operations were being erased while MLIR iterators still held references to them:

1. HandlerReplicationPass.cpp: funcOp->erase() was called inside module->walk([&](ep2::FuncOp ...)), invalidating the walker's internal iterator. The freed memory was later accessed, producing corrupted string data and the std::length_error crash.
2. GlobalToPartitionPass.cpp: global.erase() was called inside a for (auto global : moduleOp.getOps<GlobalOp>()) loop, similarly invalidating the iterator.
3. Passes.h: HandlerFullName(std::string, std::string) stored StringRef members pointing into temporary std::string parameters. Changed to accept llvm::StringRef directly.

Fix
Defer all operation erasures to after the iteration completes, using a collection vector.

Testing
Successfully compiled tests/experiments_c/nfchain.c --target rtl end-to-end, producing __handler_NET_RECV_process_packet_1.sv and __ep2top.sv. Previously crashed every time at the ep2-handler-repl pass.