Introduce clz(x) and Boost 1.83.0 in Version 0.8.31-pre.1

Yul introduces builtin clz(x) for counting leading zero bits in 256-bit words. Ethdebug adds experimental support for instructions and source locations under EOF. The assembler fixes ID typing in deeply nested subassemblies. Yul Optimizer resolves ExpressionSimplifier bugs with out-of-scope variables. Build updates require Boost 1.83.0, GCC 13.3, and Clang 18.1.3, fixing infinite recursion in boost::rational comparisons for older versions.