fix cargo check errors

[neeldug]

This Pull Request fixes/closes #1335.

It changes the following:

• moves all f64 constants NAN or Infinity to the associated version
• Parallelizes the Test262 suite

[Razican]

Test262 conformance changes:

Test result	master count	PR count	difference
Total	78,897	78,897	0
Passed	26,941	26,941	0
Ignored	15,628	15,628	0
Failed	36,328	36,328	0
Panics	0	0	0
Conformance	34.15%	34.15%	0.00%

[neeldug]

Broken tests:

test/built-ins/Number/prototype/toExponential/this-is-0-fractiondigits-is-0.js [strict mode] (previously Passed)
test/built-ins/Number/prototype/toExponential/this-is-0-fractiondigits-is-0.js (previously Passed)

For the broken tests, I ran the tests manually and they seemingly passed, unless I'm trying to run the test incorrectly?

[Razican]

Let's merge it :) I would have preferred the parallelization to go in a different PR, but the change is minimal, so let's bring it.