Rollup merge of #143738 - rocurley:float_tests_refactor_2, r=tgross35

Move several float tests to floats/mod.rs

This PR moves several tests to `floats/mod.rs`, as discussed in rust-lang/rust#141726. The tests moved are:

- `test_num_f*`
- `test_infinity`
- `test_neg_infinity`
- `test_zero`
- `test_neg_zero`
- `test_one`
- `test_is_nan`
- `test_is_infinite`
- `test_is_finite`
- `test_is_normal`
- `test_classify`

Each test is its own commit, so it may be easiest to review each commit individually.

r? tgross35

Author: samueltardieu