The merge kept this branch's PluginConfig design, which deletes
PluginDescriptor::settings, get_plugin_settings() and ctx.params, but left
references to them behind: the slic3rutils target did not build, and the
bindings test still asserted the removed ctx.params attribute.
Port the two settings tests onto PluginConfig instead of dropping them. They
guard a field bug where a cloud-metadata refresh wiped a plugin's settings and
it silently ran on its own defaults, so the equivalent properties are still
worth pinning: that a stored config survives the refresh, and that an edited
config reaches the plugin through a real dispatch.
Also defer PluginsConfigDialog's web commands off the webview script-message
callback, as PluginsDialog already does. Its remove_preset_override handler put
a modal wxMessageBox on that stack, which is the GTK crash class fixed in
b779a7bfed/f2ccbfc8b5 for the sibling dialog.
Cloud catalog records never carry [tool.orcaslicer.plugin.settings], so the
metadata merge wiped the locally-parsed settings and plugins silently ran on
their built-in defaults (ctx.params arrived empty).
