Consider using Murmur3 instead of SHA in VariationOrRollout

[rbalamohan]

https://github.com/launchdarkly/java-client/blob/master/src/main/java/com/launchdarkly/client/VariationOrRollout.java#L51

VariationOrRollout is one of the hotpath code and it internally uses SHA1 for computing hash. SHA1 is CPU intensive and is outdated as well. It would be good to consider using other hashing functions like murmur3 which is fairly CPU optimised. Guava libraries should have murmur3 IIRC.

[eli-darkly]

See PR comments. Summary: we're considering such a change, but it would require server-side changes first. I'm closing this issue since it's not something we can address in the Java SDK by itself, but we're still tracking it as a desirable future feature.