Issue #3573887: Decouple AI Migration HTML Sanitizer code into "Document Loader: HTML Processor"

Decouple HTML Sanitizer logic into the HTML Processor.

QA Steps

Run drush commands locally after reviewing the !1 (diffs)

Example

Testing out getting the main div from html source.

drush dlhp:test --content="<div class=\"main\"><p>Hello</p></div>" --container=.main'

Fetching an external url.

drush dlhp:test --url=https://example.com