Separate package and library installation

This commit satisfies required libraries after all packages have been installed,
instead of resolving and installing each required library before a package is.

Advantages:

1. not yet installed package source doesn't need to be scanned for required
   libraries or the plugin host it will run on. Reduces code duplication.
2. package and library installation/upgrade can be parallelized in a future
   version, without risk to install a library twice due to race conditions.
3. separation of concerns; low-level `install_package()` function just installs
   a package and `install_library()` just a library.

Author: deathaxe

package_control/package_manager.py

@@ -1593,31 +1593,6 @@ def install_package(self, package_name, unattended=False):
             except (FileNotFoundError):
                 pass
 
-            library_names = release.get('libraries')
-            if not library_names:
-                # If libraries were not in the channel, try the package
-                try:
-                    lib_info_json = package_zip.read(common_folder + 'dependencies.json')
-                    lib_info = json.loads(lib_info_json.decode('utf-8'))
-                except (KeyError):
-                    lib_info = {}
-                except (ValueError):
-                    console_write(
-                        '''
-                        Failed to parse the dependencies.json for "%s"
-                        ''',
-                        package_name
-                    )
-                    return False
-
-                library_names = self.select_libraries(lib_info)
-
-            if library_names:
-                self.install_libraries(
-                    library.names_to_libraries(library_names, python_version),
-                    fail_early=False
-                )
-
             if package_name != old_package_name:
                 self.rename_package(old_package_name, package_name)
 

package_control/package_tasks.py

@@ -295,6 +295,9 @@ def remove_packages(self, packages, progress=None, package_kind=''):
                 elif result is None:
                     deferred.add(package)
 
+            required_libraries = self.manager.find_required_libraries()
+            self.manager.cleanup_libraries(required_libraries=required_libraries)
+
             if num_packages == 1:
                 message = 'Package {} successfully removed'.format(list(packages)[0])
             elif num_packages == num_success:
@@ -395,6 +398,10 @@ def run_install_tasks(self, tasks, progress=None, unattended=False, package_kind
                 elif result is None:
                     package_names.remove(task.package_name)
 
+            required_libraries = self.manager.find_required_libraries()
+            self.manager.install_libraries(libraries=required_libraries, fail_early=False)
+            self.manager.cleanup_libraries(required_libraries=required_libraries)
+
             if num_packages == num_success:
                 if package_kind or num_packages > 1:
                     message = 'All {}packages successfully installed'.format(package_kind)
@@ -488,6 +495,10 @@ def run_upgrade_tasks(self, tasks, progress=None, unattended=False):
                     if package != task.available_name:
                         disable_packages[self.INSTALL].remove(task.available_name)
 
+            required_libraries = self.manager.find_required_libraries()
+            self.manager.install_libraries(libraries=required_libraries, fail_early=False)
+            self.manager.cleanup_libraries(required_libraries=required_libraries)
+
             if num_packages == num_success:
                 if num_packages > 1:
                     message = 'All packages successfully upgraded'