build: clear 237 warnings - unused lambda captures (#15417)

* build: enable /Zc:lambda for MSVC

MSVC keeps its legacy lambda processor under /std:c++17, which rejects
reading a constexpr constant inside a lambda that does not capture it
(C3493). No other compiler requires that capture, and clang reports it as
an unused one, so the two cannot both be satisfied without the flag.

/Zc:lambda selects the conforming lambda parser that clang and GCC
already use. It is implied by /std:c++20 and /permissive-, so it is only
needed while we are on C++17. clang-cl is conforming already and does not
take the flag.

It requires VS2019 16.8, so build_release_vs.bat now says 16.8+.

* build: clear 237 unused lambda capture warnings

236 captures across 81 files, 142 of them `this`. Removing an unused
capture changes no behavior; clang does not report a capture whose type
has a non-trivial destructor, so nothing held only to extend an object's
lifetime is in this set.

Nine of them are the second half of the warning, "is not required to be
captured for this use", where the capture is a const or constexpr value
the body does read. Those depend on the /Zc:lambda change in the previous
commit. One of them, in FillRectilinear.cpp, had been worked around with
an #ifndef __APPLE__ guard around the capture list, which is now gone.

GUI_ObjectTableSettings.cpp captured its reset button only to read it
inside #ifdef __WXOSX_MAC__. That branch now takes the button from the
event it is already handling.

* build: fail configure on MSVC older than 19.28 instead of dropping /Zc:lambda

cl.exe answers an unrecognized /Zc: sub-option with warning D9002 and keeps
going, so on VS2019 before 16.8 the flag is silently ignored and the build
instead dies with C3493 in FillRectilinear.cpp, nowhere near the cause.

* fix: delete three locals that are now unused

Their only remaining use was the lambda capture this branch removed. The
Clang builds set -Wno-unused-variable, so the build never flagged them.

---------

Co-authored-by: Rodrigo Faselli <162915171+RF47@users.noreply.github.com>

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -2324,7 +2324,7 @@ void ObjectList::load_modifier(const wxArrayString& input_files, ModelObject& mo
                 bool split_compound = wxGetApp().app_config->get_bool("is_split_compound");
                 model = Model::read_from_step(
                     input_file, LoadStrategy::LoadModel, nullptr, nullptr,
-                    [this, &is_user_cancel, &linear, &angle, &split_compound](Slic3r::Step& file, double& linear_value,
+                    [&is_user_cancel, &linear, &angle, &split_compound](Slic3r::Step& file, double& linear_value,
                                                                                      double& angle_value, bool& is_split) -> int {
                         if (wxGetApp().app_config->get_bool("enable_step_mesh_setting")) {
                             StepMeshDialog mesh_dlg(nullptr, file, linear, angle);
@@ -3317,7 +3317,7 @@ void ObjectList::boolean()
         }
     }
 
-    TriangleMesh mesh = Plater::combine_mesh_fff(*object, -1, [this](const std::string& msg) {return wxGetApp().notification_manager()->push_plater_error_notification(msg); });
+    TriangleMesh mesh = Plater::combine_mesh_fff(*object, -1, [](const std::string& msg) {return wxGetApp().notification_manager()->push_plater_error_notification(msg); });
 
     // add mesh to model as a new object, keep the original object's name and config
     Model* model = object->get_model();
@@ -6267,7 +6267,7 @@ void GUI::ObjectList::smooth_mesh()
     get_selection_indexes(obj_idxs, vol_idxs);
     auto object_idx = obj_idxs.front();
     ModelObject *obj{nullptr};
-    auto show_warning_dlg = [this](int cur_face_count,std::string name,bool is_part) {
+    auto show_warning_dlg = [](int cur_face_count,std::string name,bool is_part) {
         int limit_face_count = 1000000;
         if (cur_face_count > limit_face_count) {
             auto name_str = wxString::FromUTF8(name);
@@ -6280,7 +6280,7 @@ void GUI::ObjectList::smooth_mesh()
         }
         return false;
     };
-    auto show_smooth_mesh_error_dlg = [this](std::string name) {
+    auto show_smooth_mesh_error_dlg = [](std::string name) {
         auto name_str = wxString::FromUTF8(name);
         auto content  = wxString::Format(_L("\"%s\" part's mesh contains errors. Please repair it first."), name_str);
         WarningDialog dlg(static_cast<wxWindow *>(wxGetApp().mainframe), content, wxEmptyString, wxOK);