Add extension hovers to Bitbucket Server/Data Center v7+

Created by: tjkandala

Fix #24278 (closed).

• Add view resolver + DOM functions for new Bitbucket PR view.
• Use new sourcegraph/codeintellify#401 overrideTokenization to fix v6 PR view (only code views on BB Server/Data Center that aren't already tokenized)
• Allow code views to override code host toolbar styles, delete previously unused code view toolbar classes.