cgen: use standard checks for float comparisons

[UweKrueger]

Since there was only positive feedback to #5180 I've created this PR that switches to standard float checks. It also removes code that is not needed any more.

Sorry to whoever has implemented this! The work was not in vain since a very similar approach is will probably be needed for other comparison cases.

[medvednikov]

I think we should leave f32.eq() or f32.eq_epsilon or math.compare_floats() or something

[spytheman]

Sigh... This fairly known problem, will then continue to surprise novices in programming, even in V...

[UweKrueger]

@medvednikov I've added f64.eq_epsilon() and f32.eq_epsilon(). Since these are not used by default, I've spent some effort to make them work in the whole normalized range of these types (0,±FLT_MIN..±FLT_MAX, denormalized numbers < FLT_MIN might be problematic).
@spytheman surprises can be fun ;-) Honestly, I think the only way to really avoid surprises is implementing arbitrary precision symbolic math with the ability to proof the equality of two differently structured expressions. But this goes in the direction computer algebra system or formal verification and lies definitely beyond the scope of the v core language.
Once upon a time there were computer systems that used internal decimal representation of numbers (and pocket calculators do so even today). This makes at least what you see is what you get and avoids some surprises. gcc supports IEEE754 decimal floats, however due to lack of hardware support the performance is limited.

[medvednikov]

@UweKrueger thanks!

By the way I just found out that enum = 1 works, enum = Enum(1) must be required.

[dumblob]

I finally posted my "opus magnum" 😉 to strongly encourage you to rething float comparisons once again - see #5180 (comment) .