This is largely a cherry pick of #6755 with some additional fixups added where detected.
This change moves the blockchain package to a package called blocksync. Additionally, it renames the relevant uses of the term `fastsync` to `blocksync`.
closes: #9227
#### PR checklist
- [ ] Tests written/updated, or no tests needed
- [x] `CHANGELOG_PENDING.md` updated, or no changelog entry needed
- [x] Updated relevant documentation (`docs/`) and code comments, or no
documentation updates needed
* docs theme
* vuepress-theme-cosmos
* version bump
* changes to docs
* more code changes
* sidebar order fix
* moar changes
* fixed dev sessions title
* fixed dev sessions title, again
* specs should show up in sidebar
* contents cards
* version bump
* sidebar, rpc
* version bump
* custom footer and super naive search
* version
* minor change to vuepress
* move swagger file
* pre and post scripts
* build
* changed docs build process
* added deployment config
* updated versions file and added deployment filters
