Opening non-rrd files through the UI should be reflected in the StoreSource

[teh-cmc]

By allowing users to drag-and-drop/open non-rrd files in the UI, we've effectively introduced a new logging source (where logging source is broadly defined as creating a store), but we haven't reflected that in the StoreSource enum:

pub enum StoreSource {
    Unknown,

    /// The official Rerun C Logging SDK
    CSdk,

    /// The official Rerun Python Logging SDK
    PythonSdk(PythonVersion),

    /// The official Rerun Rust Logging SDK
    RustSdk {
        rustc_version: String,
        llvm_version: String,
    },

    /// Loading a file directly from disk via the CLI.
    FileFromCli {
        rustc_version: String,
        llvm_version: String,
    },

    /// Perhaps from some manual data ingestion?
    Other(String),
}

We're missing a FileFromUI entry:

    /// Loading a file directly from the UI (open or drag-and-drop).
    ///
    /// Only relevant for non-rrd files.
    FileFromUi {
        viewer_version: String,
    },

Loading a jpeg through the UI should resulting in store_source=FileFromUi and data_source=File.