Improve `kotlin.uuid.Uuid` hashcode

[FelixDes]

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Hi, dear maintainers,

I've found an issue with the new multiplatform implementation of kotlin.uuid.Uuid. Its hashCode method can be rewritten with utilizing Long.hashCode() for better readability.

[FelixDes]

The math underlying this change:

x = mostSignificantBits ^ leastSignificantBits Original code was:

int( x ) ^ int( x >> 32 )

With my change it is:

int( x ^ (x >>> 32) ) <=> int( x ) ^ int( x >>> 32 )

>>> and >> are equal in this case because the difference is in the left most bit which is truncated by int casting

[fzhinkin]

cc @qurbonzoda

[qurbonzoda]

The two implementations are indeed equivalent according to Long.hashCode() documentation: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Long.html#hashCode() I am not sure about the improved readability, it depends on whether the reader is familiar with how Long.hashCode() is implemented.

[qwwdfsad]

The readability is straightforward -- instead "hey, is it something tailored by UUID? Is it handrolled? Is it robust for hashmaps?" there is immediate "Ok, this is how the language hashes longs"

[qurbonzoda]

I've merged your commit into master manually: https://github.com/JetBrains/kotlin/commit/1fe504564ecacdbbb5b231be34355dca557f1840

Thanks for the contribution!