8229485: Add decrementExact(), incrementExact(), and negateExact() to java.lang.StrictMath Summary: three methods are added to StrictMath for consistency with Math. Tests are updated accordingly. Reviewed-by: bpb, lancea, igerasim, dfuchs, joehw, rriggs Contributed-by: Julia Boes <julia.boes@oracle.com>

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