Handle inline styles so we can tighten CSP style directive

[masaball]

Related issue: #6929

Most important changes:

• Switch to css-mini-extract-plugin for (s)css loading. The default style-loader creates inline style elements, while the extract plugin extracts the css into a file that we can then pull in via stylesheet_tag nonce: true.
• Added some hashes to the style directive. This is because Video.js dynamically creates a handful of style elements. Providing hashes for those elements seems more secure than other options but will potentially have some amount of upkeep associated with it when performing Video.js upgrades. If the hashes end up being inconsistent in future testing, we may be forced to leave style-src on unsafe_inline.