issue: #50699

Fixes #50699

## What this PR does

This PR makes JSON path predicate missing/null/type-mismatch behavior
preserve UNKNOWN consistently:

- Treats parent JSON NULL, missing nested paths, incompatible path
types, and invalid array paths as UNKNOWN instead of operator-specific
boolean constants.
- Preserves JSON stats/index validity bitmaps when returning cached
bitmap results.
- Updates parser rewrite behavior and tests that previously assumed
scalar JSON missing-path `!=` was a definite true result.
- Aligns raw, stats/index, brute-force, offset/iterative, and `NOT`
behavior around SQL-style three-valued logic.

## Verification

- `cmake -S internal/core -B cmake_build`
- `ninja -v unittest/all_tests`
- `go test -buildvcs=false -count=1
./internal/parser/planparserv2/rewriter`
- Focused C++ JSON nullable/contains suite passed 705/705.
- Additional binary-range/non-nullable JSON range/term suite passed
540/540.
- `git diff --check` passed.
- Staged diff check passed.

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Signed-off-by: Buqian Zheng <zhengbuqian@gmail.com>