Support the plain LRU policy

[tatsuya6502]

Fixes #388. (CC: @PhotonQuantum)

This PR does the followings:

• Adds a support for the plain LRU eviction policy.
• Adds a new method eviction_policy to the CacheBuilder to choose either the EvictionPolicy::tiny_lfu() or the EvictionPolicy::lru() at the cache creation time.

The TinyLFU policy will remain the default until we implement the Window TinyLFU with hill climbing.

• Upgrade the cache policy from TinyLFU to W-TinyLFU #249

[tatsuya6502]

I ran some experiments with an updated Moka driver for the Caffeine Simulator:

• Support Moka v0.12.7 with different eviction policies: TinyLFU and LRU caffeine-sim-drivers#1

I confirmed that the both the LRU and TinyLFU policies of Moka are working as expected. Their hit rates are comparable to the simulation results of the LRU and TinyLFU policies respectively.

ARC S3 trace

Policy	100,000	200,000	300,000	400,000	500,000	600,000	700,000	800,000
opt.Clairvoyant	25.42	39.79	50.92	59.96	67.09	72.97	77.57	81.27
sketch.WindowTinyLfu (1%)	12.18	23.38	33.85	43.00	51.36	59.27	65.43	70.62
linked.Lru_TinyLfu	10.63	22.89	33.96	43.18	51.50	59.41	65.58	70.91
product.Moka (TinyLFU)	10.44	22.62	33.10	42.47	50.87	58.44	64.87	70.32
linked.Lru	2.33	4.63	7.59	12.04	22.77	34.63	46.04	56.60
product.Moka (LRU)	2.33	4.63	7.59	12.04	22.77	34.63	46.04	56.60

Corda vault service large trace

Policy	200,000	400,000	600,000	800,000	1,000,000	1,200,000	1,400,000	1,600,000
opt.Clairvoyant	33.33	33.33	33.33	33.33	33.33	33.33	33.33	33.33
sketch.WindowTinyLfu (1%)	33.33	33.33	33.33	33.33	33.33	33.33	33.33	33.33
linked.Lru_TinyLfu	5.43	10.70	16.03	21.37	26.71	32.05	33.33	33.33
product.Moka (TinyLFU)	8.22	16.14	24.11	31.94	32.02	33.33	33.33	33.33
linked.Lru	33.33	33.33	33.33	33.33	33.33	33.33	33.33	33.33
product.Moka (LRU)	33.33	33.33	33.33	33.33	33.33	33.33	33.33	33.33

[tatsuya6502]

Merging.