fix: suppress side-effect-free strict equality reports

[ChargingFoxSec]

Summary

Fixes #3041.

This suppresses incorrect-equality findings in side-effect-free view/pure functions, while preserving reports for view/pure helpers that are reachable from state-changing functions.

Root cause

IncorrectStrictEquality.tainted_equality_nodes currently skips top-level functions, but does not account for function mutability. As a result, strict equality checks in external/public view query functions can be reported even when they do not gate a state transition.

Changes

• Skip view/pure functions when no non-view/pure caller can reach them.
• Keep reporting internal view helpers when they are reachable from a state-changing function.
• Add an e2e detector regression test and snapshot for the view/pure case.

Testing

• uv run pytest tests/e2e/detectors/test_detectors.py -k IncorrectStrictEquality
• uv run ruff check slither/detectors/statements/incorrect_strict_equality.py tests/e2e/detectors/test_detectors.py
• uv run ruff format --check slither/detectors/statements/incorrect_strict_equality.py tests/e2e/detectors/test_detectors.py

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