Drop internal test runner

This commit removes obsolete internal `package_control_tests` command
in favor of UnitTesting, which can be used to run them.

Default.sublime-commands

@@ -122,9 +122,5 @@
             "file": "$packages/User/Package Control.user-ca-bundle",
             "semi_transient": true
         },
-    },
-    {
-        "caption": "Package Control: Tests",
-        "command": "package_control_tests"
     }
 ]

Package Control.sublime-settings

@@ -286,7 +286,4 @@
 			]
 		}
 	},
-
-	// Enable the ability to run the tests - this is only for development
-	"enable_tests": false
 }

package_control/commands/__init__.py

@@ -17,7 +17,6 @@
 from .package_control_enable_debug_mode_command import PackageControlEnableDebugModeCommand
 from .package_control_insert_command import PackageControlInsertCommand
 from .package_control_message_command import PackageControlMessageCommand
-from .package_control_tests_command import PackageControlTestsCommand
 from .remove_channel_command import RemoveChannelCommand
 from .remove_package_command import RemovePackageCommand
 from .remove_packages_command import RemovePackagesCommand
@@ -50,7 +49,6 @@
     'PackageControlEnableDebugModeCommand',
     'PackageControlInsertCommand',
     'PackageControlMessageCommand',
-    'PackageControlTestsCommand',
     'RemoveChannelCommand',
     'RemovePackageCommand',
     'RemovePackagesCommand',

plugin.py

@@ -236,7 +236,6 @@
     '.commands.package_control_enable_debug_mode_command',
     '.commands.package_control_insert_command',
     '.commands.package_control_message_command',
-    '.commands.package_control_tests_command',
     '.commands',
 
     '.automatic_upgrader',