Add MinIO container implementation under org.testcontainers.minio

[khalilswdp]

Continues the ongoing package migration by adding a MinIO container implementation
under org.testcontainers.minio, following the same approach as the Solr (#11104)
and Cassandra (#8616) migrations.

Changes

• Add org.testcontainers.minio.MinIOContainer with an API identical to the
  existing class (constructors, withUserName, withPassword, getS3URL,
  credential getters).
• Deprecate org.testcontainers.containers.MinIOContainer via a @deprecated
  javadoc tag pointing to the new class. The deprecated class is otherwise
  untouched, so existing users are unaffected apart from a compile-time
  deprecation warning.
• Move MinIOContainerTest to org.testcontainers.minio so the documentation
  snippets (codeinclude blocks) demonstrate the new package.
• Update the codeinclude paths in docs/modules/minio.md accordingly.

Notes

• No behavior changes: the new class is a copy of the existing implementation,
  differing only in package declaration and an explicit GenericContainer import.
• Migrating user code is an import change:
  org.testcontainers.containers.MinIOContainer → org.testcontainers.minio.MinIOContainer.
• ./gradlew :testcontainers-minio:checkstyleMain :testcontainers-minio:checkstyleTest :testcontainers-minio:spotlessApply passes, and the module tests were run
  locally against Docker.