Optimize baseline and special case performance for kSmallest

[Barbarrosa]

Improve the baseline and special case performance of kSmallest.

Before:

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 26.71 ops/sec ±1.26% (48 runs sampled)

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 2.75 ops/sec ±1.76% (11 runs sampled)

After:

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 36.96 ops/sec ±1.03% (64 runs sampled)

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 3.66 ops/sec ±1.26% (14 runs sampled)

[lemire]

@Barbarrosa This is very good. Please consider my comments.

[Barbarrosa]

@lemire I updated the branch based on your comments. Here is the updated performance based on my testing today.

Before (slow)

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 25.80 ops/sec ±0.42% (46 runs sampled)

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 2.70 ops/sec ±1.92% (11 runs sampled)

Original PR (faster)

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 39.60 ops/sec ±0.95% (52 runs sampled)

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 4.06 ops/sec ±0.80% (15 runs sampled)

PR after changes (similar to Original PR)

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 39.81 ops/sec ±0.67% (53 runs sampled)

starting dynamic queue/enqueue benchmark
FastPriorityQueue--queue-and-kSmallest x 4.03 ops/sec ±1.56% (15 runs sampled)

[lemire]

Great. Merging.

[staltz]

Just a heads up (I don't have more information at the moment), this PR broke a corner case in jitdb, something about calling kSmallest and it returning undefined. I'll try to work on finding a simple reproduction and submit a test to FastPriorityQueue.

cc @arj03

[Barbarrosa]

@staltz I identified the issue, it's an overflow when requesting larger numbers of records. I'll open a PR to fix it.

[Barbarrosa]

@staltz @lemire I opened https://github.com/lemire/FastPriorityQueue.js/pull/38 to address the issue.