Fix migrating mt-[0px] to -mt-[0px] instead of the other way around

[RobinMalfait]

I was testing to upgrade tool on various random projects just to see how it behaves. Then I noticed an odd migration...

This PR fixes an issue where the upgrade tool accidentally migrated classes such as mt-[0px] to -mt-[0px]. The reason for this is because we are trying to find a replacement, and the computed signature for both of them are exactly the same.

• mt-[0px] translates to:

  .x {
    margin-top: 0px;
  }

• -mt-[0px] translates to:

  .x {
    margin-top: calc(0px * -1);
  }

  Which in turn translates to

  .x {
    margin-top: 0px;
  }

  Notice that this is 0px, not -0px.

Internally we use the roots of functional utilities to find replacements. For intellisense purposes we typically show negative versions before positive versions. This then means that we will try -mt-* before mt-*. Because of the signature above, the mt-[0px] was translated into -mt-[0px].

We could solve this in a few ways. The first thing we can try is to make sure that the signature is not the same and that -mt-[0px] actually translates into -0px not 0px.

This would solve our problem of the accidental migration. However, if we just sort the functional utilities roots such that the positive versions exist before negative version and rely on the fact that -mt-[0px] has the same signature. Then it also means that by doing that we can migrate -mt-[0px] into mt-[0px] which is even better because it's the same result and shorter.

Test plan

1. Added a test to verify that mt-[0px] does not get migrated to -mt-[0px].
2. Added a test to verify that -mt-[0px] does get migrated to mt-[0px].

[thecrypticace]

Nice and simple 👍