Perf(observableset): Remove extra clone operation on read

[tonyraoul]

Code change checklist

• Added/updated unit tests
• Updated /docs. For new functionality, at least API.md should be updated
• Verified that there is no significant performance drop (yarn mobx test:performance)

Context

within the observableset, on retriving entries/keys/values or during iteration, there is an extra Array.from operation that is causing an unwanted copy of values within memory, the significance of extra operation is amplified when considering iterator helper methods where it would read the entire range of elements within the set instead of lazy evaluation, i.e: Set.prototype.entries().take(1), or any other case when the iterator is partially retrieved Set.prototype.entries().next().

Benchmarks

Time

Use a macbook air M1 - 8GB model - plugged in, 1000 iterations

test	before	after
Set: conversion to array - 1000 elements	3.33s min - 3.41s max	2.90s min - 2.95s max
Set: conversion to array - 10000 elements	12.74s min - 12.87s max	9.10s min - 9.16s max
Set: iterator helpers - 1000 elements, take(1)	0.60s min - 0.77s max	0.31s min - 0.32s max
Set: iterator helpers - 10000 elements, take(1)	4.19s min - 4.22s max	0.31s min - 0.32s max

Memory

Mesuring the effect on memory when converting a large observableset to an array.

size	before	after
1M item	66 Mb	46 Mb
10M item	617 Mb	423 Mb

   function benchmarkMemoryUsage() {
            const beforeMemory = memoryUsage().heapUsed
            
            const obs = observable.set()
            for (let i = 0; i < 10000_000; i++) {
                obs.add(i)
            }

            const x = Array.from(obs)
            const afterMemory1 = memoryUsage().heapUsed

            console.log(`Memory diff: ${(afterMemory1 - beforeMemory) / 1000_000} Mbytes %`)
        }

[changeset-bot]

🦋 Changeset detected

Latest commit: b4d3074

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
mobx	Patch

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