[Bug][compiler-v2] Locations available in stackless bytecode are incorrect when wildcards are involved

[vineethk]

🐛 Bug

This bug pertains to compiler v2 (and the bug description should be read with that context in mind).

When we have move code involving wildcards, like let _ = x;, the AST to stackless bytecode translation does not pass on location information correctly (in particular, it is different from how location information is passed on for say let _1 = x;).

Because of this, when there are errors involved in such code, that stackless-bytecode-based checkers can report, the location provided in the error messages point to incorrect part of the code.

Consider the following example (taken from third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard2.move):

module 0xc0ffee::m {
    public fun baz() {
        let x: u64;
        let _ = x;
    }
}

Compiler v2 reports the following error (note where we point to):

error: use of unassigned local `x`
  ┌─ tests/bytecode-generator/wildcard2.move:4:13
  │
4 │         let _ = x;
  │             ^

Another similar example can be seen in third_party/move/move-compiler-v2/tests/bytecode-generator/wildcard7.exp after #12818 lands.