Rust: Value flow and taint flow through formatting strings

[paldepind]

This PR adds:

• Value flow through macro calls.
• Taint flow from arguments (including those in format strings) to format_args! to the format_args! expression itself.
• Adds to models for stdlib functions used in format!.

The original goal was to get taint through the format! macro. But since its definition uses a let statement, the issue in #18330 prevents that from working. But once that is fixed, the changes here should give flow through fomat!.

MacroCalls are now included in the CFG in post-order. Previously they where skipped over and not included in the CFG, but this caused the getMacroCall predicate on MacroExprCfgNode to never have any results. Including them in the CFG fixes that, and I don't think there's any reason to exclude them.