Use JS's == operator for JSString equality comparison

[MaxDesiatov]

This change reduces binary size of products linked with JavaScriptKit when used with Embedded Swift. By relying on reference equality and otherwise on element-wise equality it avoids going through string normalization that would add a dependency on other portions of the Swift standard library.

[github-actions]

Time Change: +268ms (2%)

Total Time: 9,730ms

Test name	Duration	Change
Serialization/JavaScript function call from Swift	133ms	+12ms (9%)	🔍
Serialization/Swift Int to JavaScript with assignment	366ms	+23ms (6%)	🔍
Serialization/Swift Int to JavaScript with call	999ms	+52ms (5%)	🔍
Serialization/Swift String to JavaScript with assignment	439ms	+25ms (5%)	🔍

View Unchanged

Test name	Duration	Change
Serialization/JavaScript function call through Wasm import	24ms	+0ms
Serialization/JavaScript function call through Wasm import with int	23ms	-0ms
Serialization/JavaScript Number to Swift Int	269ms	+8ms (2%)
Serialization/Swift String to JavaScript with call	1,078ms	+43ms (3%)
Serialization/JavaScript String to Swift String	3,578ms	+90ms (2%)
Object heap/Increment and decrement RC	2,791ms	+18ms (0%)

View Baselines

Test name	Duration
Serialization/Call JavaScript function directly	8ms
Serialization/Assign JavaScript number directly	6ms
Serialization/Call with JavaScript number directly	6ms
Serialization/Write JavaScript string directly	7ms
Serialization/Call with JavaScript string directly	5ms