Improve tests for get_blog_id_from_url()

Expand tests to cover additional cache and lookup scenarios. Explicitly test the reaction of `get_blog_id_from_url()` when `$drop = false` is passed to `wpmu_delete_blog()`. See #30080

Fixes #30088


git-svn-id: https://develop.svn.wordpress.org/trunk@30007 602fd350-edb4-49c9-b593-d223f7449a82