#446: Implement Dense representation for HLL once a threshold is reached

[the-code-innovator]

Added Benchmarks for PFADD.

Benchmarks with the current Sparse Representation in PFADD

goos: darwin
goarch: arm64
pkg: github.com/dicedb/dice/internal/eval
cpu: Apple M1 Pro
BenchmarkEvalPFADD/PFAddSize_0-8         	 3737166	       317.1 ns/op	      80 B/op	       3 allocs/op
BenchmarkEvalPFADD/PFAddSize_10-8        	  628004	      1892 ns/op	     665 B/op	      22 allocs/op
BenchmarkEvalPFADD/PFAddSize_100-8       	   64923	     18592 ns/op	    4850 B/op	     125 allocs/op
BenchmarkEvalPFADD/PFAddSize_1000-8      	    3874	    303253 ns/op	   68278 B/op	    1177 allocs/op
BenchmarkEvalPFADD/PFAddSize_10000-8     	    1576	    757984 ns/op	  160080 B/op	   10003 allocs/op
BenchmarkEvalPFADD/PFAddSize_100000-8    	     306	   3911595 ns/op	 1600081 B/op	  100003 allocs/op
PASS
ok  	github.com/dicedb/dice/internal/eval	8.562s

Fixes: #446