AWS Lambda for .NET Support

## Description

As a .NET developer I would like to build serverless Lambda application with .NET and deploy this application using AWS CDK. It is painful to design a build process which first need to build/test and package one or more Lambda functions in my project and then use lambda.Code.fromAsset(path.join(__dirname, 'out', 'package.zip')) to point to those packages. This has been beautifully solved with the [aws-lambda-go](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-lambda-go-alpha-readme.html), [aws-lambda-nodejs](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_lambda_nodejs-readme.html) and [aws-lambda-python](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-lambda-python-alpha-readme.html) L2 constructs.

## Roles

| Role | User
|---------------------|------------------------------
| Proposed by | @vlesierse
| Author(s) | @vlesierse
| API Bar Raiser |
| Stakeholders | @vlesierse

> See [RFC Process](https://github.com/aws/aws-cdk-rfcs#rfc-process) for details

## Workflow

- [x] Tracking issue created (label: `status/proposed`)
- [ ] API bar raiser assigned (ping us at [#aws-cdk-rfcs](https://cdk-dev.slack.com/archives/C025ZFGMUCD) if needed)
- [ ] Kick off meeting
- [ ] RFC pull request submitted (label: `status/review`)
- [ ] Community reach out (via Slack and/or Twitter)
- [ ] API signed-off (label `api-approved` applied to pull request)
- [ ] Final comments period (label: `status/final-comments-period`)
- [ ] Approved and merged (label: `status/approved`)
- [ ] Execution plan submitted (label: `status/planning`)
- [ ] Plan approved and merged (label: `status/implementing`)
- [ ] Implementation complete (label: `status/done`)

---

> Author is responsible to progress the RFC according to this checklist, and
apply the relevant labels to this issue so that the RFC table in README gets
updated.

Start with the linked aws-lambda-go, aws-lambda-nodejs, and aws-lambda-python construct documentation, then review the RFC checklist and the existing lambda.Code.fromAsset workflow described here. Define the .NET construct's scope and API through the RFC process; done means the proposal reaches API approval and the required implementation planning stages.

Written by the indexing model from the issue text.