Add Int64/UInt64 to Bigint slow conversion

[kateinoigakukun]

Int64 -> BigInt conversion can be done by passing two i32 without i64-bigint integration feature. This is a slow path, but useful for environments that have BigInt but don't have i64-bigint integration.

[github-actions[bot]]

Time Change: -276ms (1%)

Total Time: 19,142ms

Test name	Duration	Change
Serialization/Call JavaScript function directly	3ms	+1ms	🚨
Serialization/Assign JavaScript number directly	3ms	-1ms	🎉
Serialization/Call with JavaScript number directly	6ms	+3ms (47%)	🚨
Serialization/Write JavaScript string directly	2ms	-1ms (52%)	🏆
Serialization/Call with JavaScript string directly	4ms	+2ms (44%)	🚨
Serialization/JavaScript function call through Wasm import	19ms	+1ms (6%)	🔍
Serialization/JavaScript function call through Wasm import with int	17ms	-3ms (19%)	👏

View Unchanged

| Test name | Duration | Change | | :--- | :---: | :---: | | Serialization/JavaScript function call from Swift | 567ms | +7ms (1%) | | Serialization/Swift Int to JavaScript with assignment | 388ms | -1ms | | Serialization/Swift Int to JavaScript with call | 2,120ms | -44ms (2%) | | Serialization/JavaScript Number to Swift Int | 585ms | -3ms (0%) | | Serialization/Swift String to JavaScript with assignment | 447ms | -1ms | | Serialization/Swift String to JavaScript with call | 2,243ms | -23ms (1%) | | Serialization/JavaScript String to Swift String | 5,388ms | -151ms (2%) | | Object heap/Increment and decrement RC | 7,350ms | -63ms (0%) |

[kateinoigakukun]

Yes, the variant choice would be made in caller side for now.

[kateinoigakukun]

BTW, some of the benchmark cases are too fast and cause meaningless reports...