support void in standard result type, and fix RPC

[afsalthaj]

Fixes #181

SDK standard result types had two issues: One is void was not supported similar to the bug in user defined result type. Second is, RPC never worked even after making it supported in type mappings. Both are fixed

Stderr:

thread '<unnamed>' (1) panicked at src/internal.rs:276:41:
Exception during awaiting call result for guest.invoke:
JavaScript error: Failed to invoke corge in agent bar-agent("foos")
Stack:
    at invokeAndAwait (@golemcloud/golem-ts-sdk:5824:27)

import {
    BaseAgent,
    Result,
    agent,
    prompt,
    description, Client,
} from '@golemcloud/golem-ts-sdk';

@agent()
class CounterAgent extends BaseAgent {
    private readonly name: string;
    private readonly client: Client<BarAgent>;

    constructor(name: string) {
        super()
        this.name = name;
        this.client = BarAgent.get(name);
    }

    async foo(input: Result<number, void>): Promise<Result<number, void>> {
        return await this.client.qux(input);
    }

    async bar(input: Result<void, number>): Promise<Result<void, number>> {
        return await this.client.corge(input);
    }

    async baz(input: Result<void, void>): Promise<Result<void, void>> {
        return await this.client.grault(input);
    }
}


@agent()
class BarAgent extends BaseAgent {
    private readonly name: string;
    private value: number = 0;

    constructor(name: string) {
        super()
        this.name = name;
    }

    async qux(input: Result<number, void>): Promise<Result<number, void>> {
        return input
    }

    async corge(input: Result<void, number>): Promise<Result<void, number>> {
        return input
    }

    async grault(input: Result<void, void>): Promise<Result<void, void>> {
        return input
    }

}

Once the new ts-sdk is released, will add these tests along with the ones in #216 (comment)

[afsalthaj]

This is very similar to non sdk result type bug and same fixes. Merging and closing the issue