Error Handling controller and LoadPolicies

[robwalch]

This PR will...

Implement an ErrorController to handle error events before and after other controllers. On ERROR, ErrorController is responsible for level switching, falling back to redundant streams, and escalating errors to fatal when there is no action to take.

• Handle missed probe transmux probe with with FRAG_PARSING_ERROR
• Handle encrypted init segment and subtitle decryption failure with FRAG_DECRYPT_ERROR
• Remove delay when retrying after timeout
• Trigger FRAG_LOADING after request is made
• All ERROR event data type must include an error property
• Add stats to network loader error callbacks to allow error handling to use request timing
• Remove use of console.warn from mp4-tools
• Add missing TypeScript type exports
• Switch Pathways after all fallback options are exhausted
• Failed Pathways go into a penalty box for 5 minutes

Why is this Pull Request needed?

Improve error handling and consolidate error handling logic so that it is easier to follow, and so that it can be replaced with a custom controller.

Completes Content Steering by implementing Pathway penalty and switching on error.

Are there any points in the code the reviewer needs to double check?

Resolves issues:

• Fixes No Error Event Attempting to Play Unsupported Video #5011
• Fixes Interrupting buffering with stopLoad() and then restarting with startLoad() causes a transition to the lowest level #5230
• Fixes r.assert is not a function error on npm package #5218
• Closes RT-754: Remove assert from development builds #5221

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md