Separate ui/base/interaction into an independent BUILD file

The impact of this change on WebView2Mac is positive but relatively minor. WebView2Mac primarily uses the ui/base/interaction functionality indirectly through the components/remote_cocoa/app_shim component. Specific impacts include: 1) Build dependency optimization – the remote_cocoa component now only needs to depend on the smaller interaction module instead of the entire ui/base, which may slightly improve build speed; 2) Modularization improvement – this separation makes dependencies clearer and more precise, helping to reduce unnecessary dependencies; 3) Full functional compatibility – all interaction-related classes and interfaces (such as ElementIdentifier, ElementTracker, TrackedElement, etc.) remain unchanged, with only the export macro changed from UI_BASE to UI_BASE_INTERACTION; 4) No functional impact on the core classes used by WebView2Mac (such as HostingNSWindowBridge, HostingApplicationBridge, etc.). This is a purely refactoring change and will not affect any existing functionality of WebView2Mac.