Fix a few bugs in vParquet2 structural operators

[mdisibio]

What this PR does:
A few fixes in the structural operators:

1. Need to skip over spans with broken nesting. This is detected as any value of either span == 0. Without this it was falsely identifying matches on partial traces where the spans had broken nesting
2. Sibling operator would falsely identify a span as its own sibling if it was present in multiple spansets. I.e. { .foo} ~ {.foo} because each input technically had the same parent. There are two ways to fix this, and I chose the more efficient one. Theoretically we could loading both Parent and Left and ensure Lefts are different (not same spans). However instead I am just checking struct pointers to ensure not the same *span. This works until the TraceQL engine starts making multiple passes over a file (which is not the plan and may be never).
3. There was also a small typo in DescendantOf that could have led to more false positives. I never saw this in the wild.

Which issue(s) this PR fixes:
Fixes #2658

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[mdisibio]

The typo was the third var in this statement s.nestedSetLeft -> s.nestedSetRight