Remove jstype=string from .proto and replace Long with Bigintin js-sdk

[JOOHOJANG]

What would you like to be added:
Remove jstype=JS_STRING notation from resources.proto and replace Long with Bigint in js-sdk
AS-IS

message ChangeID {
  ....
  int64 server_seq = 2 [jstype = JS_STRING];
  int64 lamport = 3 [jstype = JS_STRING];
  .....
}

TO-BE

message ChangeID {
  ....
  int64 server_seq = 2 
  int64 lamport = 3 
  .....
}

Why is this needed:
Currently, we're using jstype=JS_STRING notation in resources.proto due to javascript's int64 expression.
Since javascript support Bigintfrom ES2020, now we can remove jstype=JS_STRING notation from resources.proto and replace Long with Bigint.

I tested in some environments and it works well.

[Aswinr24]

Can I pick up this Issue? Would love to work on this

[Aswinr24]

So this issue basically needs two PRs right @hackerwins, one addressing the jstype=string issue in this main repository and the other related to replacing long with BigInt for the yorkie js-sdk repository ?