Rollup merge of #79227 - sasurau4:test/move-cell-test-to-lib-core, r=jyn514
Rollup merge of #79227 - sasurau4:test/move-cell-test-to-lib-core, r=jyn514

Remove const_fn_feature_flags test

## Overview

Helps with #76268

I found `const_fn_feature_flags` is targeting feature-gate and remove it.

r? ``@matklad``

aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust