Function load_plugins_from_dir 

pub fn load_plugins_from_dir(
    dir: &Path,
    builder: &mut PluginRegistryBuilder,
) -> Vec<PluginLoadResult>

Load all plugin shared libraries from dir and register them with builder.

Scans dir for files with the platform-appropriate extension (.so, .dylib, .dll). Each library is loaded, its build declaration is compared with this razeri’s, and its registration function is called only when the two match.

Returns one PluginLoadResult per library file found.