Make JSObject conform to ExpressibleByDictionaryLiteral

[MaxDesiatov]

The change improves compatibility with Embedded Swift by providing an alternative type: JSDictionary. Unlike the existing dictionary type, this new type doesn't rely on the existing Hashable conformance of String, but allows reuse of existing JSObject dictionary subscripts, reducing binary size of products that link with this library.

[github-actions]

Time Change: -180ms (1%)

Total Time: 9,806ms

Test name	Duration	Change
Serialization/JavaScript function call through Wasm import	24ms	-2ms (7%)	✅
Serialization/JavaScript Number to Swift Int	261ms	-18ms (6%)	✅

View Unchanged

Test name	Duration	Change
Serialization/JavaScript function call through Wasm import with int	23ms	-1ms
Serialization/JavaScript function call from Swift	129ms	-2ms (1%)
Serialization/Swift Int to JavaScript with assignment	337ms	-11ms (3%)
Serialization/Swift Int to JavaScript with call	975ms	-24ms (2%)
Serialization/Swift String to JavaScript with assignment	422ms	-18ms (4%)
Serialization/Swift String to JavaScript with call	1,054ms	-29ms (2%)
Serialization/JavaScript String to Swift String	3,739ms	-76ms (2%)
Object heap/Increment and decrement RC	2,808ms	-4ms (0%)

View Baselines

Test name	Duration
Serialization/Call JavaScript function directly	9ms
Serialization/Assign JavaScript number directly	6ms
Serialization/Call with JavaScript number directly	8ms
Serialization/Write JavaScript string directly	7ms
Serialization/Call with JavaScript string directly	5ms