Complete the plugin settings removal after the feat/plugin-feature merge

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.

src/slic3r/plugin/PluginFsUtils.cpp

@@ -467,7 +467,10 @@ bool parse_pep723_toml(const std::string& toml_content,
             if (trimmed == "[tool.orcaslicer.plugin]") {
                 section = TomlSection::OrcaPlugin;
             } else if (trimmed == "[tool.orcaslicer.plugin.settings]") {
-                section = TomlSection::OrcaPluginSettings; // per-plugin params table
+                // Legacy table, superseded by PluginConfig. Recognized so its keys are ignored
+                // rather than falling through to Root, where a stray dependencies/requires-python
+                // key inside it would be parsed as package metadata.
+                section = TomlSection::OrcaPluginSettings;
             } else {
                 section = TomlSection::Root; // Unknown section — skip.
             }

src/slic3r/plugin/pluginTypes/slicingPipeline/SlicingPipelinePluginCapability.cpp

@@ -2,7 +2,6 @@
 #include "SlicingPipelinePluginCapabilityTrampoline.hpp"
 #include "slic3r/plugin/PluginBindingUtils.hpp" // config_value_or_none
 #include "libslic3r/libslic3r.h"    // unscale<>, live SCALING_FACTOR
-#include <pybind11/stl.h>           // std::map<std::string,std::string> -> dict for ctx.params
 
 namespace py = pybind11;
 namespace Slic3r {
@@ -31,7 +30,7 @@ void SlicingPipelinePluginCapability::RegisterBindings(py::module_& module, py::
         // ctx.object are None; instead ctx.gcode_path / ctx.host / ctx.output_name are set and the plugin
         // edits the file at ctx.gcode_path IN PLACE. May fire more than once per slice (file export and/or
         // upload each fire once, on separate working copies) and its output is not reflected in the G-code
-        // preview (the viewer maps the pre-post-process file). ctx.config_value()/ctx.params still work.
+        // preview (the viewer maps the pre-post-process file). ctx.config_value() still works.
         .value("psGCodePostProcess", SlicingPipelineStepPlugin::psGCodePostProcess)
         .export_values();