Implement del statement for subscript deletion

[friendlymatthew]

This PR adds support for the del statement on subscripted objects, which enable deletion of list elements and dict entries through the del foo['bar'] syntax

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing py-delitem (2a21db6) with main (7909646)}

Summary

✅ 11 untouched benchmarks

[friendlymatthew]

This is a very harmless and branchless way of doing:

let normalized_index = if index < 0 { index + len } else { index };

The idea being:

• if index < 0, then mask is -1 (all bits set)
• if index >= 0, mask = 0, so we add 0