fix(core): amplify configure with storage path type issue

[ashwinkumar6]

Description of changes

Amplify configure with storage, with multiple buckets with unique paths throws a type error Type 'undefined' is not assignable to type 'Record<string, string[] | undefined>. This PR loosens this type to avoid this error.

Description of how you validated changes

• Updated unit test to check parsing logic for multiple buckets
• Tested that the following with amplify.configure does not throw any type error

	"storage": {
		"aws_region": "us-west-2",
		"bucket_name": "mock-bucket-1",
		"buckets": [
			{
				"name": "mock-bucket-1",
				"bucket_name": "bucket1",
				"aws_region": "us-west-2",
				"paths": {
					"sub/*": {
						"authenticated": ["get", "list"]
					},
					"public/*": {
						"guest": ["get", "list", "write", "delete"],
						"authenticated": ["write", "get", "list", "delete"]
					}
				}
			},
			{
				"name": "mock-bucket-2",
				"bucket_name": "bucket2",
				"aws_region": "us-west-2",
				"paths": {
					"public/*": {
						"guest": ["get", "list", "write", "delete"],
						"authenticated": ["write", "get", "list", "delete"]
					}
				}
			}
		]
	}

• amplify.getConfig returns the correct config

Checklist

• PR description included
• yarn test passes
• Unit Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

Checklist for repo maintainers

• Verify E2E tests for existing workflows are working as expected or add E2E tests for newly added workflows
• New source file paths included in this PR have been added to CODEOWNERS, if appropriate

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[ashwinkumar6]

note:
We have added Partial for AmplifyOutputs here but not for the Amplify singleton in itself. Adding Partial to the singleton would mean we would need to update additional APIs that consume path since they expect a stricter type from the singleton.

Hence the additional parsing logic above in parseAmplifyOutputs.ts is required
(same goes auth userGroups as well)

[ashwinkumar6]

The sanitization step is required to convert Partial<Record<string, ...>> type to Record<string, ...> by removing undefined values. i.e remove Partial.