Add keyboard shortcuts to the project manager

- Ctrl + N: New Project
- Ctrl + I: Import Project
- Ctrl + S: Scan for Projects
- Ctrl + E: Edit Project
- Ctrl + R: Run Project
- F2: Rename Project
- Delete: Remove Project
  - Already implemented previously, but moved to use `ED_SHORTCUT()`.

Note that depsite using `ED_SHORTCUT()`, these shortcuts won't appear
in the Editor Settings' Shortcuts dialog and won't be remappable since
the project manager code isn't run in the editor.

(cherry picked from commit 9bda49e03014549370074ac52a3b7bac1d421c86)

editor/project_manager.cpp

@@ -1848,9 +1848,6 @@ void ProjectManager::_unhandled_input(const Ref<InputEvent> &p_ev) {
 			case KEY_ENTER: {
 				_open_selected_projects_ask();
 			} break;
-			case KEY_DELETE: {
-				_erase_project();
-			} break;
 			case KEY_HOME: {
 				if (_project_list->get_project_count() > 0) {
 					_project_list->select_project(0);
@@ -2491,12 +2488,14 @@ ProjectManager::ProjectManager() {
 
 	Button *open = memnew(Button);
 	open->set_text(TTR("Edit"));
+	open->set_shortcut(ED_SHORTCUT("project_manager/edit_project", TTR("Edit Project"), KEY_MASK_CMD | KEY_E));
 	tree_vb->add_child(open);
 	open->connect("pressed", this, "_open_selected_projects_ask");
 	open_btn = open;
 
 	Button *run = memnew(Button);
 	run->set_text(TTR("Run"));
+	run->set_shortcut(ED_SHORTCUT("project_manager/run_project", TTR("Run Project"), KEY_MASK_CMD | KEY_R));
 	tree_vb->add_child(run);
 	run->connect("pressed", this, "_run_project");
 	run_btn = run;
@@ -2505,6 +2504,7 @@ ProjectManager::ProjectManager() {
 
 	Button *scan = memnew(Button);
 	scan->set_text(TTR("Scan"));
+	scan->set_shortcut(ED_SHORTCUT("project_manager/scan_projects", TTR("Scan Projects"), KEY_MASK_CMD | KEY_S));
 	tree_vb->add_child(scan);
 	scan->connect("pressed", this, "_scan_projects");
 
@@ -2520,22 +2520,26 @@ ProjectManager::ProjectManager() {
 
 	Button *create = memnew(Button);
 	create->set_text(TTR("New Project"));
+	create->set_shortcut(ED_SHORTCUT("project_manager/new_project", TTR("New Project"), KEY_MASK_CMD | KEY_N));
 	tree_vb->add_child(create);
 	create->connect("pressed", this, "_new_project");
 
 	Button *import = memnew(Button);
 	import->set_text(TTR("Import"));
+	import->set_shortcut(ED_SHORTCUT("project_manager/import_project", TTR("Import Project"), KEY_MASK_CMD | KEY_I));
 	tree_vb->add_child(import);
 	import->connect("pressed", this, "_import_project");
 
 	Button *rename = memnew(Button);
 	rename->set_text(TTR("Rename"));
+	rename->set_shortcut(ED_SHORTCUT("project_manager/rename_project", TTR("Rename Project"), KEY_F2));
 	tree_vb->add_child(rename);
 	rename->connect("pressed", this, "_rename_project");
 	rename_btn = rename;
 
 	Button *erase = memnew(Button);
 	erase->set_text(TTR("Remove"));
+	erase->set_shortcut(ED_SHORTCUT("project_manager/remove_project", TTR("Remove Project"), KEY_DELETE));
 	tree_vb->add_child(erase);
 	erase->connect("pressed", this, "_erase_project");
 	erase_btn = erase;