oss: Upgrade Aliyun OSS SDK to v2 and add RRSA support

[suikammd]

hanges:

• Bumped github.com/aliyun/alibabacloud-oss-go-sdk-v2 to the latest v2 SDK and removed legacy v1 dependency.
• Updated providers/oss API calls to conform with the new pointer-and-context-based signature of v2.
• Introduced credentials-go to support RRSA (RAM Role for Service Account).
• Added explicit RRSA configuration fields (role_arn, oidc_provider_arn, oidc_token_file_path, role_session_name) in the Config struct.
• Implemented a credential provider fallback logic:
  1. Use static AK/SK if explicitly provided.
  2. Use explicit RRSA (OIDC role) config if provided.
  3. Fallback to the default credential provider chain (loading OIDC token from environment variables).
• Removed rigid legacy v1 references from clientutil/parse_test.go and replaced them with canonical headers strings, making it provider-agnostic.

Verification:

• Verified standard compilation by running go build ./...
• Verified test suite by running go test -v ./providers/oss/... ensuring no existing functional regressions.