ARTEMIS-6144 Improve getPagedResult

[GChuf]

Benchmarks below:

Benchmark	addressCount	Throughput (main)	Throughput (6144)	Δ Throughput	Alloc (main, B/op)	Alloc (6144, B/op)	Δ Alloc
testAllResults	1000	1,127.29 ops/s	3,583.19 ops/s	+217.9%	37,502.19	47,313.95	+26.2%
testAllResults	10000	82.95 ops/s	219.52 ops/s	+164.6%	449,604.60	460,263.58	+2.4%
testFirstPage	1000	1,126.65 ops/s	3,661.16 ops/s	+225.0%	22,958.20	47,289.91	+106.0%
testFirstPage	10000	80.90 ops/s	229.92 ops/s	+184.2%	280,597.19	460,238.15	+64.0%
testMiddlePage	1000	1,127.60 ops/s	3,591.73 ops/s	+218.5%	23,422.20	47,529.95	+102.9%
testMiddlePage	10000	81.81 ops/s	219.18 ops/s	+167.9%	281,651.85	460,479.60	+63.5%

[GChuf]

Ready for review.
After a bunch of sanity checks:
The JMH tests show a positive improvement in speed, a bit higher memory usage though - but the mem usage is small.
JProfiler shows reduction in relative cpu usage from 20-25% to about 6-10%.
The majority of the benefits, and all the extra mem usage come from fieldCache = new IdentityHashMap<>(array.length). Otherwise I was getting better memory numbers before I added the IdentityHashMap.