perf(collection): optimisations (#10552)

* perf: `merge()`: deduplicate boolean checks

* perf: `toSorted()`: remove redundant closure

* perf: `last[Key]()`: order of operations

- do not perform iterable-to-array until required
- test ! before <

* perf: `{at,keyAt}()`: manually iterate to target

* perf: `first[Key]()`: avoid `Array.from()`

* perf: `map()`: avoid `Array.from()`

* perf: `random[Key]()`: avoid `Array.from()`

* test: `.{at,keyAt}()` indices

* perf: `last[Key]()`: use `.at()`/`.keyAt()` for single element

* perf: `first[Key]()`: use iterable-to-array if returning all

* perf: `random[Key]()`: use `{at,keyAt}()` for single value

- skip iterable-to-array for returning single value
- short-circuit if amount or collection size is zero

* perf: `random[Key]()`: use Durstenfeld shuffle

* refactor: `{key,keyAt}()`: reorder index check

---------

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

packages/collection/__tests__/collection.test.ts

@@ -70,12 +70,20 @@ describe('at() tests', () => {
 		expect(coll.at(0)).toStrictEqual(1);
 	});
 
+	test('positive non-integer index', () => {
+		expect(coll.at(1.5)).toStrictEqual(2);
+	});
+
 	test('negative index', () => {
 		expect(coll.at(-1)).toStrictEqual(3);
 	});
 
+	test('negative non-integer index', () => {
+		expect(coll.at(-2.5)).toStrictEqual(2);
+	});
+
 	test('invalid positive index', () => {
-		expect(coll.at(4)).toBeUndefined();
+		expect(coll.at(3)).toBeUndefined();
 	});
 
 	test('invalid negative index', () => {
@@ -432,12 +440,20 @@ describe('keyAt() tests', () => {
 		expect(coll.keyAt(0)).toStrictEqual('a');
 	});
 
+	test('positive non-integer index', () => {
+		expect(coll.keyAt(1.5)).toStrictEqual('b');
+	});
+
 	test('negative index', () => {
 		expect(coll.keyAt(-1)).toStrictEqual('c');
 	});
 
+	test('negative non-integer index', () => {
+		expect(coll.keyAt(-2.5)).toStrictEqual('b');
+	});
+
 	test('invalid positive index', () => {
-		expect(coll.keyAt(4)).toBeUndefined();
+		expect(coll.keyAt(3)).toBeUndefined();
 	});
 
 	test('invalid negative index', () => {