feat(type-safe-api): generate lambda handler stubs based on model trait

[cogwirrel]

This change adds a new configuration option handlers which allows users to opt in to generating lambda handler projects for java, python, and/or typescript, ready-configured with packaging tasks for use in a lambda function.

Handler stubs are generated for operations annotated with the @handler trait in Smithy (or the x-handler vendor extension in OpenAPI), only generating the handler stubs for the chosen language for each operation. Documentation to come once this feature has been further fleshed out!

For now, as a very quick reference, here's how you'd reference a lambda in each language from these packages:

    new Api(this, 'api', {
      defaultAuthorizer: Authorizers.iam(),
      integrations: {
        someTypescriptOp: {
          integration: Integrations.lambda(new Function(this, 'someTypescriptOp', {
            runtime: Runtime.NODEJS_18_X,
            code: Code.fromAsset('../api/handlers/typescript/dist/lambda/some-typescript-op'),
            handler: 'index.handler',
          })),
        },
        someJavaOp: {
          integration: Integrations.lambda(new Function(this, 'someJavaOp', {
            runtime: Runtime.JAVA_17,
            code: Code.fromAsset('../api/handlers/java/dist/java/com/generated/api/api-java-handlers/0.0.0/api-java-handlers-0.0.0.jar'),
            handler: 'com.generated.api.apijavahandlers.handlers.SomeJavaOpHandler',
          })),
        },
        somePythonOp: {
          integration: Integrations.lambda(new Function(this, 'somePythonOp', {
            runtime: Runtime.PYTHON_3_11,
            code: Code.fromAsset('../api/handlers/python/dist/lambda'),
            handler: 'api_python_handlers.some_python_op.handler',
          })),
        },
      },
    });

Once the handlers have been initially generated, they are never overwritten (much like projen sample code, except generated at build time). If users move or rename generated handlers, they will be generated again - so if not sticking to the default project structure it's recommended to add the @handler trait, build, rename/refactor, remove the @handler trait, and continue.

Coming soon:

• Generate tests
• Generate default interceptors

[agdimech]

Nice work buddy - this is looking fantastic, can't wait to try it!