Adds an idiomatic rule that suggests using reduce(into:) when a for ... in loop is encountered that references a collection variable (of type Array, Set or Dictionary).

This is mostly to encourage immutability, higher-order functions and to prevent dangling vardecls.

The canonical triggering example is:

            var result: [SomeType] = []
            for eachN in someSequence {
                ↓result[someIndex] = eachN
            }

The rule does not check for mutating methods on sequences within a for ... in statement.