Fix needless_range_loop false positive with nested indexing

[XhesicaFrost]

needless_range_loop could emit an incorrect suggestion for nested indexing
expressions such as a[sum % 5][i].

In this case, the container indexed by the loop variable may change between
iterations, so replacing the range loop with an iterator over the base
container would change the program's semantics.

This detects non-constant container-selection indices while walking nested
index expressions and suppresses the lint in those cases. The existing behavior
is preserved when the loop variable selects the outer container.

A regression test for the reported case and a corresponding positive test have
been added.

fixes #17432

changelog: [needless_range_loop]: avoid false positives when indexing dynamically selected nested containers

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