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
* Don't use state sync for nodes starting at initial height.
* Also remove stopped containers when cleaning up.
* Start nodes in order of startAt, mode, name to avoid full nodes starting before their seeds.
* Tweak network waiting to avoid halts caused by validator changes and perturbations.
* Disable most tests for seed nodes, which aren't always able to join consensus.
* Disable `blockchain/v2` due to known bugs.
This was a missing test case from the old P2P tests removed in #5453, which makes sure that all nodes are able to peer with each other regardless of how they discover peers.
Fixes#2795, since the default CI testnet uses a combination of (partially meshed) persistent peers and PEX-based seed nodes.
