[lldb] Constant-resolve operands to `getelementptr`

Operands to `getelementptr` can be constants or constant expressions. Check
that all operands can be constant-resolved and resolve them during the
evaluation. If some operands can't be resolved as constants -- the expression
evaluation will fallback to JIT.

Fixes: https://bugs.llvm.org/show_bug.cgi?id=52449

Reviewed By: #lldb, shafik

Differential Revision: https://reviews.llvm.org/D113498