Auto merge of #7350 - camsteffen:suspicious, r=flip1995

Add suspicious group

changelog: Introduce `clippy::suspicious` 🤔 group and move several lints into the group

Closes #6366. CC #6626.

A number of lints are moved from each of `correctness`, `style` and `complexity` groups. Notably I didn't move `suspicious_splitn` since I think that is a `correctness` lint despite the name.

Lints moved to `clippy::suspicious`:
* `blanket_clippy_restriction_lints` (was `clippy::style`)
* `empty_loop` (was `clippy::style`)
* `eval_order_dependence` (was `clippy::complexity`)
* `float_equality_without_abs` (was `clippy::correctness`)
* `for_loops_over_fallibles` (was `clippy::correctness`)
* `misrefactored_assign_op` (was `clippy::complexity`)
* `mut_range_bound` (was `clippy::complexity`)
* `mutable_key_type` (was `clippy::correctness`)
* `suspicious_arithmetic_impl` (was `clippy::correctness`)
* `suspicious_assignment_formatting` (was `clippy::style`)
* `suspicious_else_formatting` (was `clippy::style`)
* `suspicious_map` (was `clippy::complexity`)
* `suspicious_op_assign_impl` (was `clippy::correctness`)
* `suspicious_unary_op_formatting` (was `clippy::style`)