Add More Checks to Plugin Directory Admin Review Tools

[Ipstenu]

We should improve the Admin Tools for the directory to include some of the more common items we flag as possibly problematic.

High level usually means we can't approve it at all (or without serious work)
Medium level may be okay
Low level is informational

I'm attaching a VERY ROUGH and un-pretty first pass at a patch to the review tools metabox to get started. It's based on @coffee2code's tool (which I use but have not seen the code for yet), modernized for the new world.

The things we need to scan for are:

Low

• Restricted names - slugs we've determined are indicative of abuse
• New users
• The plugin is the user’s first (first-time authors may need more handholding and review)
• The user has no home URL defined in their profile
• The user’s home URL is 'weird' (blogger, tumblr, etc are weird for developers)

Medium

• Slug length (too long/too short)
• Restricted slugs or spammer-abused ones
• User account was registered less than 3 days ago
• Username ends in numbers
• The user’s home URL is at a generic blog service
• User was rejected for this very plugin before - Not written. I'm not sure if we should, since this changes dramatically in the new world.

High

• Reserved names - commonly abused trademark/slugs like google, woocommerce, jetpack, etc.
• User is banned from logging into WP.org

Special

• Slug use. If the slug is already hitting our API while the plugin is in draft, that means it's being used out in the wild. We should be more respectful of that and alert based on usage. The code for this is non-existent. I framed it out since I have no idea yet how to get the data yet.

[Ipstenu]

First pass at more tools

[obenland]

In 6543:

Plugins: Add basic set of plugin checks

Props Ipstenu.
Fixes #2350.