Fixes#1870Fixes#1863
A validation has been added to **PutBucketCors** for `CORSRule.AllowedOrigins`. The `AllowedOrigins` list can no longer be empty—otherwise a **MalformedXML** error is returned. Additionally, each origin is now validated to ensure it does not contain more than one wildcard.
A similar validation has been added for `AllowedMethods`. The list must not be empty, or a **MalformedXML** error is returned. Previously, empty method values (e.g., `[]string{""}`) were incorrectly treated as valid. This has been fixed, and an **UnsupportedCORSMethod** error is now returned.
All the integration tests used to be in a single file, which had become large, messy, and difficult to maintain. These changes split `tests.go` into multiple files, organized by logical test groups.