Allow configuration to choose `BigInt` over `Long.js` for `int64` types

[Will-Mann-16]

Is your feature request related to a problem? Please describe.

Inability to configure parsing int64 types to BigInt over Long.js or String - .

Describe the solution you'd like

At the moment the choices for when we can handle int64/uint64 types are only Long or String - Now with the ES2020 inclusion of BigInt which is much more compatible and doesn't rely on a third party package. We're also using ts-proto to codegen values and they give us the option but unfortunately it's not available on this library AFAIK.

Describe alternatives you've considered

We can use strings or Long.js but for us it makes much more sense in our use case to maintain using the Number type and using the BigInt option for us as it's much more futureproof.

Additional context

We're using Nest.js here with these package versions:

@nestjs/microservices: ^11.1.17
@grpc/grpc-js: ^1.14.3
@grpc/proto-loader: ^0.8.0
@nestjs/common: ^11.0.1
@nestjs/core: ^11.0.1

[murgatroid99]

The @grpc/proto-loader library is a fairly thin wrapper around the protobufjs library, and that's what controls this behavior. Unfortunately, the PR to add that functionality there (protobufjs/protobuf.js#1908) has been open for 3 years without any response.