Allow executing async functions from TypeScript REST framework

[iliyan-velichkov]

For example:

import { Controller, Post } from "sdk/http"
import { ConcatenateParamsDTO, ConcatenateResultDTO } from "./concatenate-dto"
import { execute } from "/string-util/dist/run.mjs"

@Controller
class SnowflakeService {

    @Post("/concatenate")
    public async concatenate(params: ConcatenateParamsDTO): Promise<ConcatenateResultDTO> {
        const abapParams = {
            iv_string1: params.param1,
            iv_string2: params.param2
        };
        const result = await execute(abapParams);
        console.log("Result in REST: " + result);
        return {
            result: result
        };
    }

}

Motivation: I want to be able to call async function from the REST and return the response synchronously.
Dirigible project reference: https://github.com/codbex/abap-samples/blob/15e7b3426d585cb35bf320e8fa625bf18b43f0e7/snowflake-api-project/api/SnowflakeService.ts#L29