fix(vyper): model loop bounds and range arguments correctly

[zloglevel]

Summary

Fix Vyper loop modeling in the CFG and SlithIR generation.

Root Cause

Vyper loops were modeled with an inclusive upper bound:

counter_var <= len(iterable)
counter_var <= range_end

This caused one extra modeled iteration and could produce an invalid access at iterable[len(iterable)].

For two-argument range(start, end), Slither also initialized the artificial counter to 0 and used the first argument as the endpoint. This did not match Vyper's half-open range semantics.

Changes

• Use counter_var < len(iterable) for array iteration.
• Use counter_var < end for range(end).
• Initialize the artificial counter with start for range(start, end).
• Use the second positional argument as the endpoint.
• Preserve Vyper's bound keyword behavior without treating it as the range endpoint.
• Add regression coverage for dynamic array iteration and two-argument ranges.
• Update affected Vyper CFG/SlithIR snapshots.

Testing

30 passed
ruff check passed
git diff --check passed

[CLAassistant]

All committers have signed the CLA.