GeezerVison

Summary

Fix the SQL standard boundary calculation in binary_substring3___ for non-positive starting offsets, fix 1-based indexing in binary_overlay4____, and add unit tests.

Fixes #7830.

Root Cause & Problem

In crates/sqllib/src/binary.rs:

1. binary_substring3___(source, left, count) handles left < 1 by clamping start = 0 but leaving count unchanged. Under SQL 1-based substring semantics (such as in string.rs), the extraction window starts at index left with length count. Any part of the window preceding position 1 should be omitted, yielding an effective count of (count + left - 1).max(0). Because count was unadjusted, non-positive start values extracted more bytes than expected (or extracted prefix bytes when the entire window was non-positive).
2. binary_overlay4____ invoked binary_substring3___(source.clone(), 0, position - 1) with 0 instead of 1, which previously succeeded only because left = 0 was clamped to 0 without adjusting count.
3. Both binary_substring2__ and binary_substring3___ were consuming source.data and allocating via .into_iter().skip(...).take(...).collect(), which is inefficient compared to direct slice construction via ByteArray::new(&slice[start..end]).

Technical Solution

1. In binary_substring3___, calculate the extracted count for left < 1 using (count.saturating_add(left).saturating_sub(1)).max(0) to prevent integer overflow while correctly clamping non-positive starting windows.
2. Replace iterator-based collection with direct byte slicing on source.as_slice().
3. In binary_overlay4____, pass 1 as the 1-based start position for the prefix substring.
4. Add comprehensive unit test coverage in crates/sqllib/src/binary.rs testing standard 1-based offsets, non-positive starts (left = 0, left < 0), zero/negative count, edge-case integer extremes (i32::MIN, i32::MAX), and binary_overlay.

Test Plan

• Run targeted unit tests in Rust 1.99 container: cargo test -p feldera-sqllib --lib binary:: (passed, 34 tests ok)
• Run code formatting check: rustfmt --check crates/sqllib/src/binary.rs (passed with code 0)