perf(redis): Don't re-encode string when computing hash (#3838)

When caching values in redis, we compare the hash of the value
we're about to write against the value already in the cache to
avoid writing unchanged values again.

The hash function we're using is expensive as it encodes the string
to bytes before hashing it. Per the documentation of the
putString function, it is only useful for cross-language compatibility
and we should instead use putUnencodedChars for much better performance
when this is not needed.

cats/cats-redis/src/main/java/com/netflix/spinnaker/cats/redis/cache/RedisCache.java

@@ -15,8 +15,6 @@
  */
 package com.netflix.spinnaker.cats.redis.cache;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
-
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.collect.Iterables;
@@ -442,7 +440,7 @@ private boolean hashCheck(
       boolean hasTtl) {
     if (options.isHashingEnabled() && !hasTtl) {
       final String hash =
-          Hashing.sha1().newHasher().putString(serializedValue, UTF_8).hash().toString();
+          Hashing.sha1().newHasher().putUnencodedChars(serializedValue).hash().toString();
       final String existingHash = hashes.get(id);
       if (hash.equals(existingHash)) {
         return true;