Allow `suboptimal_flops` in const functions
This PR allows `clippy::suboptimal_flops` in constant functions. The check also effects the `clippy::imprecise_flops` lint logic. However, this doesn't have any effects as all functions checked for are not const and can therefore not be found in such functions.
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changelog: [`suboptimal_flops`]: No longer triggers in constant functions
Closes: rust-lang/rust-clippy#8004