Fix a wrong (oversized) initial capacity for the internal hash map

[tatsuya6502]

I misunderstood what the initial capacity would do for cht::SegmentedHashMap. I thought it was the initial capacity of the entire hash map, but the cht author meant it was the initial capacity of each segment in the hash map. Since Moka uses SegmentedHashMap with currently hard-coded number of segments 64, setting the initial capacity using Moka's CacheBuilder results the hash map 64 times bigger than desired.

This PR changes the initial capacity of moka::cht::SegmentedHashMap to be the capacity of the entire hash map.

[tatsuya6502]

Merging