Remove deprecated LRUBlockCache

[Amemeda]

LruBlockCache was depreacted in #4920 and replaced with TinyLfuBlockCache, this pr removes LruBlockCache and related code:

• LruBlockCache.java: Deleted
• LruBlockCacheConfiguration.java: Deleted
• LruBlockCacheManager.java: Deleted
• TestlLruBlockCache.java: Deleted
• BlockCacheFactoryTest: Updated to remove deprecated test testCreateLruBlockCacheFactory()
• CachedBlock.java: Deleted (only uses were in deleted test file)
• CacheBlockQueue.java: Deleted (only uses were in deleted test file)
• HeapSize.java: Deleted (only uses were in deleted test file)
• TestCachedBlockQueue: Deleted, only tested lru cache using the above 3 files
• SynchronizedLoadingBlockCache.java: Moved from lru subfolder to tinylfu subfolder. Still used elsewhere in code.
• blockfile.cache.lru subfolder: Deleted

Closes #4921

[Amemeda]

There are 4 files remaining in the cache.lru subfolder where all the lru files were deleted from. The only usage of these files is in TestCachedBlockQueue.java which is testing using lru.CachedBlock.java. All tests in this file still pass with the LRU deleted. So I am wondering, should TestCachedBlockQueue.java be deleted along with the remaining 4 files in lru package? Or I can refactor the remaining 4 files from the lru package, probably to rename the package to util or something similar.

[dlmarion]

I think you can remove TestCachedBlockQueue as well

[Amemeda]

There is a method in BlockCacheManager.java that still has documentation referencing LRU. Unsure if this needs to be updated to TinyLFU or its talking about a different LRU like the LRU Map I see throughout the code

   /**
     * This method provides a way for a cache implementation to access arbitrary configuration set
     * by a user.
     *
     * <p>
     * When running in a tserver, returns all Accumulo properties that have a prefix of
     * {@code tserver.cache.config.<prefix>.<type>.} or
     * {@code tserver.cache.config.<prefix>.default.} with values for specific cache types
     * overriding defaults.
     *
     * <p>
     * When running in a scan server, returns all Accumulo properties that have a prefix of
     * {@code sserver.cache.config.<prefix>.<type>.} or
     * {@code sserver.cache.config.<prefix>.default.} with values for specific cache types
     * overriding defaults.
     *
     * <p>
     * For example assume the following data is in Accumulo's system config and the plugin is
     * running in a tserver.
     *
     * <pre>
     * tserver.cache.config.lru.default.evictAfter=3600
     * tserver.cache.config.lru.default.loadFactor=.75
     * tserver.cache.config.lru.index.loadFactor=.55
     * tserver.cache.config.lru.data.loadFactor=.65
     * </pre>
     *
     * <p>
     * If this method is called with {@code prefix=lru} and {@code type=INDEX} then it would return
     * a map with the following key values. The load factor setting for index overrides the default
     * value.
     *
     * <pre>
     * evictAfter=3600
     * loadFactor=.55
     * </pre>
     *
     * @param prefix A unique identifier that corresponds to a particular BlockCacheManager
     *        implementation.
     */
    Map<String,String> getProperties(String prefix, CacheType type);