Config schema: Define AWS "stream" function event properties

[medikoo]

Use case description

It'll be nice to have stream event fully covered by schema validation

Proposed solution

Follow up to #6562, with which only schema placeholder for event was configured.

Define schema of all stream event properties

Should be done directly in: lib/plugins/aws/package/compile/events/stream/index.js:

serverless/lib/plugins/aws/package/compile/events/stream/index.js

Lines 14 to 17 in d403d9c

	// TODO: Complete schema, see https://github.com/serverless/serverless/issues/8034
	this.serverless.configSchemaHandler.defineFunctionEvent('aws', 'stream', {
	anyOf: [{ type: 'string' }, { type: 'object' }],
	});