build: clear 50 warnings - pessimizing moves and null checks that cannot fail (#15408)

* build: remove std::move that blocks copy elision

std::move wrapped around a temporary, or around a local being returned,
stops the compiler constructing it in place. Each edit is the fix clang
suggests, which is to delete the std::move call and keep its argument.

Three of the 39 sites save a move, the two return std::move(local) in
Print.cpp and TreeSupport.cpp:2749. The rest are equivalent either way
and match how the codebase already writes this elsewhere.

Clears 39 -Wpessimizing-move warnings.

* build: drop null checks on references and this

A reference cannot be bound to null and this cannot be null, so the
compiler folds these conditions to true and drops the guard. Seven are
if (&bitmap && bitmap.IsOk()), where IsOk() already does the work; two
test this directly. The guarded code runs either way, so removing the
dead operand changes nothing.

Clears 11 -Wundefined-bool-conversion warnings.

src/slic3r/Utils/PresetUpdater.cpp

@@ -1198,7 +1198,7 @@ Updates PresetUpdater::priv::get_config_updates(const Semver &old_slic3r_version
                     version.config_version = cache_ver;
                     version.comment        = description;
                     // Orca: update vendor.json
-                    updates.updates.emplace_back(std::move(file_path), std::move(path_in_vendor.string()), std::move(version), vendor_name, changelog, "", force_update, false);
+                    updates.updates.emplace_back(std::move(file_path), path_in_vendor.string(), std::move(version), vendor_name, changelog, "", force_update, false);
                     //Orca: update vendor folder
                     updates.updates.emplace_back(cache_profile_path / vendor_name, vendor_path / vendor_name, Version(), vendor_name, "", "", force_update, true);
                 } else {