Add format string resolution provider APIs

[plafosse]

Summary

• add the public C++ FormatStringResolutionProvider interface with platform-aware type resolution and confidence preservation
• provide the C-style format string implementation as a standalone core plugin that registers itself from CorePluginInit
• expose provider registration, enumeration, lookup, and resolution through Python
• expose the same provider surface through Rust with balanced callback and type ownership

The corresponding core and workflow changes are in binaryninja#1732.

Why

Format string analysis was previously fixed to built-in behavior and the C-style provider was only available when tests explicitly registered it. This makes providers pluggable and ensures the bundled C-style implementation is loadable in headless sessions.

Validation

• standalone core plugin loaded by bundled headless bnpython3
• Python provider tests: 3 passed
• Rust provider tests: 3 passed
• Rust formatting, clippy with warnings denied, and documentation generation passed
• complete parent Python suite: 6,082 passed, 273 skipped, 5 deselected, 119 subtests passed