Apply random float error

[LorrensP-2158466]

This partially tries to fix #3555 (does not include the pow operations)

this just does apply_random_float_error on the results of the intrinsics.
Things changed from original:

• seperated the sqrtf* intrinsics to make the implementation cleaner, since applying the error was not required
• changes the way we do approximation checks, instead of using the epsilon technique, we use ULP.
• create the relative errors of 16ULP using ulp_err_scale, which does -(F::PRECISION - 1 - n for a 2^n ULP error.
• adds a test test_non_determinism which tests a lot of non-deterministic operations with the same input to check if they are almost but not entirely equal.

[RalfJung]

Please also add a test (as a new function in tests/pass/float.rs) that checks for non-determinism by running the same operation multiple times and ensuring we get different (but similar) results.

[RalfJung]

Rounding is fully precise, it should not get any error.

[LorrensP-2158466]

Yes, I caught that and fixed it locally

[RalfJung]

Suggested change

	// no host floats for sqrt
	// Sqrt is specified to be fully precise.

(same below for sqrtf64)

[LorrensP-2158466]

Almost done I think.

I have 1 TODO left, inside of the non-determinism test, it is about this:

Please also add a test (as a new function in tests/pass/float.rs) that checks for non-determinism by running the same operation multiple times and ensuring we get different (but similar) results.

Should we do an assert_ne! test on the results, because it is possible that the same error is applied to 2 separate operations that we then check. Maybe it is possible to count these exactly equal results and if it is the same as the amount of checks we can safely say it is deterministic and should fail the test?.

[LorrensP-2158466]

@rustbot ready

[RalfJung]

Should we do an assert_ne! test on the results, because it is possible that the same error is applied to 2 separate operations that we then check. Maybe it is possible to count these exactly equal results and if it is the same as the amount of checks we can safely say it is deterministic and should fail the test?.

I think the easiest way is something like this; you can do that with a closure returning any PartialEq type instead of bool.

[LorrensP-2158466]

@rustbot ready