Move objectfs checks to check API classes, include checks in admin settings

[matthewhilton]

Since Moodle 4.4 https://tracker.moodle.org/browse/MDL-67898 is integrated, allowing you to show check API results https://moodledev.io/docs/4.4/apis/subsystems/check in the admin settings very easily.

Currently objectfs rolls this itself, for example:

moodle-tool_objectfs/settings.php

Lines 162 to 165 in c4ba44f

	if ($objectfspage) {
	$testconn = $client->test_connection();
	$connstatus = $testconn->success;
	}

The reason for rolling itself is probably only due to the fact that objectfs is older than the check API.

Will help resolve #543