Migrate away from class-transfomer

This is a rethought version of my previous ticket https://github.com/aws-cloudformation/cloudformation-cli-typescript-plugin/issues/68

To resummarize the issues with `class-transformer`:

* The serialization breaks down in the face of unsupported CloudFormation JSON Schema Features, and increases complexity since JSON Schema features must be manually mapped to the Class Transformer equivalent.
* It ties the implementation to TypeScript's decorators which are soon to be completely deprecated and redesigned entirely, and results in a data model that might be foreign to a lot of JavaScript developers today (outside angular and nestjs)
* Because of the above, it prevents JavaScript from working (though I'd personally always encourage TS over JS) (https://github.com/aws-cloudformation/cloudformation-cli-typescript-plugin/issues/8)
* ~The project isn't also super alive right now: https://github.com/typestack/class-transformer/issues/1272~ Possibly no longer as valid, it looks like the projects might be getting new maintainers.

The updated proposal proposes swapping `class-transformer` with three components:

* The package [camelcase-keys](https://www.npmjs.com/package/camelcase-keys) to handle the CloudFormation-to-JS object key camelcasing.
* The package [AJV](https://www.npmjs.com/package/ajv) to handle validating the incoming event properties, provide friendly(er) error messages, as well as [automatic type conversion](https://ajv.js.org/coercion.html)
* The package [json-schema-to-typescript](https://www.npmjs.com/package/json-schema-to-typescript) to handle consuming the resource definition and outputting type information for a richer experience.

While a very large change, it would uncouple this plugin from TypeScript and an unmaintained library while hopefully simplifying the Dev UX of developing a resource in typescript.

For example, a simple handler like the template default would become (example greatly appreviated):

```typescript
// handlers.ts
import { Resource, TypeConfiguration } from "./.generated/models";
import { createResource, ProgressEvent, exceptions } from '@amazon-web-services-cloudformation/cloudformation-cli-typescript-lib';

const { entrypoint, testEntrypoint } = createResource({
typeName: Resource.TypeName,
schema: Resource.Schema,
// Type information for all the below is automatically infered
async create({ session, properties, request, logger, typeConfiguration }) {
// Example:
try {
const { apiKey } = typeConfiguration;
const response = await fetch(`https://api.someservice.com`, {
method: 'POST',
headers: { 'x-api-key': apiKey },
body: { ...properties },
});
const { id } = await response.json();
properties.id = id;
// else handle error
} catch(err) {
logger.log(err);
// exceptions module lets CloudFormation know the type of failure that occurred
throw new exceptions.InternalFailure(err.message);
// this can also be done by returning a failed progress event
// return ProgressEvent.failed(HandlerErrorCode.InternalFailure, err.message);
}
return properties;
},
/* more handlers.... */
async list({ properties, typeConfiguration }) {
/* ...some list code... */
// Just return a plain array of models, validate via typescript & ajv
return [/* list of plain old javascript models */];
},
});

export { entrypoint, testEntrypoint };

```

This also externalizes a lot of concerns unnecessary to the user code, infers a lot more of type information automatically, and makes developing resource types much less mentally onerous allowing developers to focus on business logic.

It would require more work with the SDK and generated code however.

首先审查 issue 68 和提议的 handlers.ts 示例，然后检查 issue 所述需要更改的 SDK 和生成代码。在评估 camelcase-keys、AJV 和 json-schema-to-typescript 之前，跟踪当前的 class-transformer 集成并确定受影响的入口点。完成的标准是：plugin 不再依赖 class-transformer，支持提议的 JavaScript 和 TypeScript 工作流，并包含所需的 SDK 和生成代码更改。

由索引模型根据 Issue 内容生成。