[IR] Rename Call annotations to attrs

[tlopex]

This PR renames tirx::CallNode::annotations to attrs, matching the existing Relax CallNode::attrs convention.
Previously, TIRX Call metadata was stored in a Map<String, Any> field named annotations. This PR makes it a first-class Attrs field instead, so call-level metadata follows the same representation and naming style as Relax calls.

[gemini-code-assist]

Code Review

This pull request refactors the tirx.Call expression by replacing the annotations field with attrs (of type Attrs) across both C++ and Python APIs. This change updates the AST nodes, serialization, printers, various transformations, and associated unit tests. The reviewer suggested updating the type annotation of attrs in the Python Call class to ir.Attrs | None to correctly handle cases where no attributes are provided and prevent static type checking issues.