Added behaviour test for $pull,$pop,$max,$[<identifier>]

[afn7081]

Add behavior tests for $max, $pop, $pull, $[]

Comprehensive compat-functional tests covering:
- $max: type comparison, cross-type ordering, NaN, dates, missing fields
- $pop: first/last, empty array, nested paths, invalid values
- $pull: exact match, conditional ($gte, $in), document match, nested
- $[<identifier>]: basic filters, scalar arrays, multi, findAndModify

2 divergences tracked with engine_xfail markers:
- $pop on non-array: error code 2 instead of 14 (TypeMismatch)
- $[<identifier>] invalid identifier: accepts instead of rejecting

All tests stable across 5 serial iterations.

[documentdb-triage-tool]

🤖 Auto-triaged by documentdb-triage-tool.

Applied: compatibility test, enhancement
Project fields suggested: Component test-coverage · Priority P2 · Effort L · Status Needs Review
Confidence: 0.88 (mixed)

Reasoning

component from path globs (test-coverage); effort from diff stats (1318+0 LOC, 4 files); LLM: Adds comprehensive compatibility/behavior test coverage for multiple update operators ($max, $pop, $pull, $[identifier]) with documented divergences, touching multiple test files across one component.

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[eerxuan]

Please claim the tracking issue before raise PR, we are seeing overlapping effort across PRs. Also can you start with issues with "Second pass"? Amazon team is working through First pass features. We planned 48 features in this sprint, will claim the issues shortly.